diff --git a/pkg/apis/authentication/types.go b/pkg/apis/authentication/types.go
index bf65f1407c0..8a474ccf9d7 100644
--- a/pkg/apis/authentication/types.go
+++ b/pkg/apis/authentication/types.go
@@ -21,6 +21,15 @@ import (
 	"k8s.io/kubernetes/pkg/api/unversioned"
 )
 
+const (
+	// ImpersonateUserHeader is used to impersonate a particular user during an API server request
+	ImpersonateUserHeader = "Impersonate-User"
+
+	// ImpersonateGroupHeader is used to impersonate a particular group during an API server request.
+	// It can be repeated multipled times for multiple groups.
+	ImpersonateGroupHeader = "Impersonate-Group"
+)
+
 // +genclient=true
 // +nonNamespaced=true
 // +noMethods=true
diff --git a/pkg/apiserver/handler_impersonation.go b/pkg/apiserver/handler_impersonation.go
new file mode 100644
index 00000000000..9aedf237eb1
--- /dev/null
+++ b/pkg/apiserver/handler_impersonation.go
@@ -0,0 +1,139 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package apiserver
+
+import (
+	"net/http"
+
+	"github.com/golang/glog"
+
+	"k8s.io/kubernetes/pkg/api"
+	authenticationapi "k8s.io/kubernetes/pkg/apis/authentication"
+	"k8s.io/kubernetes/pkg/auth/authorizer"
+	"k8s.io/kubernetes/pkg/auth/user"
+	"k8s.io/kubernetes/pkg/httplog"
+	"k8s.io/kubernetes/pkg/serviceaccount"
+)
+
+// WithImpersonation is a filter that will inspect and check requests that attempt to change the user.Info for their requests
+func WithImpersonation(handler http.Handler, requestContextMapper api.RequestContextMapper, a authorizer.Authorizer) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		requestedUser := req.Header.Get(authenticationapi.ImpersonateUserHeader)
+		if len(requestedUser) == 0 {
+			if len(req.Header[authenticationapi.ImpersonateGroupHeader]) > 0 {
+				glog.V(4).Infof("attempt to impersonate groups without impersonating a user: %v", req.Header[authenticationapi.ImpersonateGroupHeader])
+				forbidden(w, req)
+				return
+			}
+
+			handler.ServeHTTP(w, req)
+			return
+		}
+
+		impersonationRequests := buildImpersonationRequests(requestedUser, req.Header[authenticationapi.ImpersonateGroupHeader])
+
+		ctx, exists := requestContextMapper.Get(req)
+		if !exists {
+			forbidden(w, req)
+			return
+		}
+		requestor, exists := api.UserFrom(ctx)
+		if !exists {
+			forbidden(w, req)
+			return
+		}
+
+		// if groups are not specified, then we need to look them up differently depending on the type of user
+		// if they are specified, then they are the authority
+		groupsSpecified := len(req.Header[authenticationapi.ImpersonateGroupHeader]) > 0
+
+		// make sure we're allowed to impersonate each thing we're requesting.  While we're iterating through, start building username
+		// and group information
+		username := ""
+		groups := []string{}
+		for _, impersonationRequest := range impersonationRequests {
+			actingAsAttributes := &authorizer.AttributesRecord{
+				User:            requestor,
+				Verb:            "impersonate",
+				APIGroup:        impersonationRequest.GetObjectKind().GroupVersionKind().Group,
+				Namespace:       impersonationRequest.Namespace,
+				Name:            impersonationRequest.Name,
+				ResourceRequest: true,
+			}
+
+			switch impersonationRequest.GetObjectKind().GroupVersionKind().GroupKind() {
+			case api.Kind("ServiceAccount"):
+				actingAsAttributes.Resource = "serviceaccounts"
+				username = serviceaccount.MakeUsername(impersonationRequest.Namespace, impersonationRequest.Name)
+				if !groupsSpecified {
+					// if groups aren't specified for a service account, we know the groups because its a fixed mapping.  Add them
+					groups = serviceaccount.MakeGroupNames(impersonationRequest.Namespace, impersonationRequest.Name)
+				}
+
+			case api.Kind("User"):
+				actingAsAttributes.Resource = "users"
+				username = impersonationRequest.Name
+
+			case api.Kind("Group"):
+				actingAsAttributes.Resource = "groups"
+				groups = append(groups, impersonationRequest.Name)
+
+			default:
+				glog.V(4).Infof("unknown impersonation request type: %v", impersonationRequest)
+				forbidden(w, req)
+				return
+			}
+
+			allowed, reason, err := a.Authorize(actingAsAttributes)
+			if err != nil || !allowed {
+				glog.V(4).Infof("Forbidden: %#v, Reason: %s, Error: %v", req.RequestURI, reason, err)
+				forbidden(w, req)
+				return
+			}
+		}
+
+		newUser := &user.DefaultInfo{
+			Name:   username,
+			Groups: groups,
+			Extra:  map[string][]string{},
+		}
+		requestContextMapper.Update(req, api.WithUser(ctx, newUser))
+
+		oldUser, _ := api.UserFrom(ctx)
+		httplog.LogOf(req, w).Addf("%v is acting as %v", oldUser, newUser)
+
+		handler.ServeHTTP(w, req)
+	})
+}
+
+// buildImpersonationRequests returns a list of objectreferences that represent the different things we're requesting to impersonate.
+// Each request must be authorized against the current user before switching contexts
+func buildImpersonationRequests(requestedUser string, requestedGroups []string) []api.ObjectReference {
+	impersonationRequests := []api.ObjectReference{}
+
+	if namespace, name, err := serviceaccount.SplitUsername(requestedUser); err == nil {
+		impersonationRequests = append(impersonationRequests, api.ObjectReference{Kind: "ServiceAccount", Namespace: namespace, Name: name})
+	} else {
+		impersonationRequests = append(impersonationRequests, api.ObjectReference{Kind: "User", Name: requestedUser})
+	}
+
+	for _, group := range requestedGroups {
+		impersonationRequests = append(impersonationRequests, api.ObjectReference{Kind: "Group", Name: group})
+	}
+
+	return impersonationRequests
+}
diff --git a/pkg/apiserver/handler_impersonation_test.go b/pkg/apiserver/handler_impersonation_test.go
new file mode 100644
index 00000000000..228405afc54
--- /dev/null
+++ b/pkg/apiserver/handler_impersonation_test.go
@@ -0,0 +1,256 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package apiserver
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"sync"
+	"testing"
+
+	"k8s.io/kubernetes/pkg/api"
+	authenticationapi "k8s.io/kubernetes/pkg/apis/authentication"
+	"k8s.io/kubernetes/pkg/auth/authorizer"
+	"k8s.io/kubernetes/pkg/auth/user"
+)
+
+type impersonateAuthorizer struct{}
+
+func (impersonateAuthorizer) Authorize(a authorizer.Attributes) (authorized bool, reason string, err error) {
+	user := a.GetUser()
+
+	switch {
+	case user.GetName() == "system:admin":
+		return true, "", nil
+
+	case user.GetName() == "tester":
+		return false, "", fmt.Errorf("works on my machine")
+
+	case user.GetName() == "deny-me":
+		return false, "denied", nil
+	}
+
+	if len(user.GetGroups()) > 0 && user.GetGroups()[0] == "wheel" && a.GetVerb() == "impersonate" && a.GetResource() == "users" {
+		return true, "", nil
+	}
+
+	if len(user.GetGroups()) > 0 && user.GetGroups()[0] == "sa-impersonater" && a.GetVerb() == "impersonate" && a.GetResource() == "serviceaccounts" {
+		return true, "", nil
+	}
+
+	if len(user.GetGroups()) > 0 && user.GetGroups()[0] == "regular-impersonater" && a.GetVerb() == "impersonate" && a.GetResource() == "users" {
+		return true, "", nil
+	}
+
+	if len(user.GetGroups()) > 1 && user.GetGroups()[1] == "group-impersonater" && a.GetVerb() == "impersonate" && a.GetResource() == "groups" {
+		return true, "", nil
+	}
+
+	return false, "deny by default", nil
+}
+
+func TestImpersonationFilter(t *testing.T) {
+	testCases := []struct {
+		name                string
+		user                user.Info
+		impersonationUser   string
+		impersonationGroups []string
+		expectedUser        user.Info
+		expectedCode        int
+	}{
+		{
+			name: "not-impersonating",
+			user: &user.DefaultInfo{
+				Name: "tester",
+			},
+			expectedUser: &user.DefaultInfo{
+				Name: "tester",
+			},
+			expectedCode: http.StatusOK,
+		},
+		{
+			name: "impersonating-error",
+			user: &user.DefaultInfo{
+				Name: "tester",
+			},
+			impersonationUser: "anyone",
+			expectedUser: &user.DefaultInfo{
+				Name: "tester",
+			},
+			expectedCode: http.StatusForbidden,
+		},
+		{
+			name: "impersonating-group-without-user",
+			user: &user.DefaultInfo{
+				Name: "tester",
+			},
+			impersonationGroups: []string{"some-group"},
+			expectedUser: &user.DefaultInfo{
+				Name: "tester",
+			},
+			expectedCode: http.StatusForbidden,
+		},
+		{
+			name: "disallowed-group",
+			user: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"wheel"},
+			},
+			impersonationUser:   "system:admin",
+			impersonationGroups: []string{"some-group"},
+			expectedUser: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"wheel"},
+			},
+			expectedCode: http.StatusForbidden,
+		},
+		{
+			name: "allowed-group",
+			user: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"wheel", "group-impersonater"},
+			},
+			impersonationUser:   "system:admin",
+			impersonationGroups: []string{"some-group"},
+			expectedUser: &user.DefaultInfo{
+				Name:   "system:admin",
+				Groups: []string{"some-group"},
+				Extra:  map[string][]string{},
+			},
+			expectedCode: http.StatusOK,
+		},
+		{
+			name: "allowed-users-impersonation",
+			user: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"regular-impersonater"},
+			},
+			impersonationUser: "tester",
+			expectedUser: &user.DefaultInfo{
+				Name:   "tester",
+				Groups: []string{},
+				Extra:  map[string][]string{},
+			},
+			expectedCode: http.StatusOK,
+		},
+		{
+			name: "disallowed-impersonating",
+			user: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"sa-impersonater"},
+			},
+			impersonationUser: "tester",
+			expectedUser: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"sa-impersonater"},
+			},
+			expectedCode: http.StatusForbidden,
+		},
+		{
+			name: "allowed-sa-impersonating",
+			user: &user.DefaultInfo{
+				Name:   "dev",
+				Groups: []string{"sa-impersonater"},
+				Extra:  map[string][]string{},
+			},
+			impersonationUser: "system:serviceaccount:foo:default",
+			expectedUser: &user.DefaultInfo{
+				Name:   "system:serviceaccount:foo:default",
+				Groups: []string{"system:serviceaccounts", "system:serviceaccounts:foo"},
+				Extra:  map[string][]string{},
+			},
+			expectedCode: http.StatusOK,
+		},
+	}
+
+	requestContextMapper = api.NewRequestContextMapper()
+	var ctx api.Context
+	var actualUser user.Info
+	var lock sync.Mutex
+
+	doNothingHandler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		currentCtx, _ := requestContextMapper.Get(req)
+		user, exists := api.UserFrom(currentCtx)
+		if !exists {
+			actualUser = nil
+			return
+		}
+
+		actualUser = user
+	})
+	handler := func(delegate http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Errorf("Recovered %v", r)
+				}
+			}()
+			lock.Lock()
+			defer lock.Unlock()
+			requestContextMapper.Update(req, ctx)
+			currentCtx, _ := requestContextMapper.Get(req)
+
+			user, exists := api.UserFrom(currentCtx)
+			if !exists {
+				actualUser = nil
+				return
+			} else {
+				actualUser = user
+			}
+
+			delegate.ServeHTTP(w, req)
+		})
+	}(WithImpersonation(doNothingHandler, requestContextMapper, impersonateAuthorizer{}))
+	handler, _ = api.NewRequestContextFilter(requestContextMapper, handler)
+
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	for _, tc := range testCases {
+		func() {
+			lock.Lock()
+			defer lock.Unlock()
+			ctx = api.WithUser(api.NewContext(), tc.user)
+		}()
+
+		req, err := http.NewRequest("GET", server.URL, nil)
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tc.name, err)
+			continue
+		}
+		req.Header.Add(authenticationapi.ImpersonateUserHeader, tc.impersonationUser)
+		for _, group := range tc.impersonationGroups {
+			req.Header.Add(authenticationapi.ImpersonateGroupHeader, group)
+		}
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tc.name, err)
+			continue
+		}
+		if resp.StatusCode != tc.expectedCode {
+			t.Errorf("%s: expected %v, actual %v", tc.name, tc.expectedCode, resp.StatusCode)
+			continue
+		}
+
+		if !reflect.DeepEqual(actualUser, tc.expectedUser) {
+			t.Errorf("%s: expected %#v, actual %#v", tc.name, tc.expectedUser, actualUser)
+			continue
+		}
+	}
+}
diff --git a/pkg/apiserver/handlers.go b/pkg/apiserver/handlers.go
index 696a3522d71..35d4e5af789 100644
--- a/pkg/apiserver/handlers.go
+++ b/pkg/apiserver/handlers.go
@@ -32,9 +32,7 @@ import (
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/errors"
 	"k8s.io/kubernetes/pkg/auth/authorizer"
-	"k8s.io/kubernetes/pkg/auth/user"
 	"k8s.io/kubernetes/pkg/httplog"
-	"k8s.io/kubernetes/pkg/serviceaccount"
 	"k8s.io/kubernetes/pkg/util/runtime"
 	"k8s.io/kubernetes/pkg/util/sets"
 )
@@ -462,75 +460,6 @@ func (r *requestAttributeGetter) GetAttribs(req *http.Request) authorizer.Attrib
 	return &attribs
 }
 
-func WithImpersonation(handler http.Handler, requestContextMapper api.RequestContextMapper, a authorizer.Authorizer) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		requestedSubject := req.Header.Get("Impersonate-User")
-		if len(requestedSubject) == 0 {
-			handler.ServeHTTP(w, req)
-			return
-		}
-
-		ctx, exists := requestContextMapper.Get(req)
-		if !exists {
-			forbidden(w, req)
-			return
-		}
-		requestor, exists := api.UserFrom(ctx)
-		if !exists {
-			forbidden(w, req)
-			return
-		}
-
-		actingAsAttributes := &authorizer.AttributesRecord{
-			User:            requestor,
-			Verb:            "impersonate",
-			APIGroup:        api.GroupName,
-			Resource:        "users",
-			Name:            requestedSubject,
-			ResourceRequest: true,
-		}
-		if namespace, name, err := serviceaccount.SplitUsername(requestedSubject); err == nil {
-			actingAsAttributes.Resource = "serviceaccounts"
-			actingAsAttributes.Namespace = namespace
-			actingAsAttributes.Name = name
-		}
-
-		authorized, reason, err := a.Authorize(actingAsAttributes)
-		if err != nil {
-			internalError(w, req, err)
-			return
-		}
-		if !authorized {
-			glog.V(4).Infof("Forbidden: %#v, Reason: %s", req.RequestURI, reason)
-			forbidden(w, req)
-			return
-		}
-
-		switch {
-		case strings.HasPrefix(requestedSubject, serviceaccount.ServiceAccountUsernamePrefix):
-			namespace, name, err := serviceaccount.SplitUsername(requestedSubject)
-			if err != nil {
-				forbidden(w, req)
-				return
-			}
-			requestContextMapper.Update(req, api.WithUser(ctx, serviceaccount.UserInfo(namespace, name, "")))
-
-		default:
-			newUser := &user.DefaultInfo{
-				Name: requestedSubject,
-			}
-			requestContextMapper.Update(req, api.WithUser(ctx, newUser))
-		}
-
-		newCtx, _ := requestContextMapper.Get(req)
-		oldUser, _ := api.UserFrom(ctx)
-		newUser, _ := api.UserFrom(newCtx)
-		httplog.LogOf(req, w).Addf("%v is acting as %v", oldUser, newUser)
-
-		handler.ServeHTTP(w, req)
-	})
-}
-
 // WithAuthorizationCheck passes all authorized requests on to handler, and returns a forbidden error otherwise.
 func WithAuthorizationCheck(handler http.Handler, getAttribs RequestAttributeGetter, a authorizer.Authorizer) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {