diff --git a/pkg/labels/selector.go b/pkg/labels/selector.go
index 0845d82305f..c35da49ac3a 100644
--- a/pkg/labels/selector.go
+++ b/pkg/labels/selector.go
@@ -20,6 +20,8 @@ import (
 	"fmt"
 	"sort"
 	"strings"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
 )
 
 // Selector represents a label selector.
@@ -105,6 +107,48 @@ func (t andTerm) String() string {
 	return strings.Join(terms, ",")
 }
 
+// Operator represents a key's relationship
+// to a set of values in a Requirement.
+// TODO: Should also represent key's existence.
+type Operator int
+
+const (
+	IN Operator = iota + 1
+	NOT_IN
+)
+
+// LabelSelector only not named 'Selector' due
+// to name conflict until Selector is deprecated.
+type LabelSelector struct {
+	Requirements []Requirement
+}
+
+type Requirement struct {
+	key       string
+	operator  Operator
+	strValues util.StringSet
+}
+
+func (r *Requirement) Matches(ls Labels) bool {
+	switch r.operator {
+	case IN:
+		return r.strValues.Has(ls.Get(r.key))
+	case NOT_IN:
+		return !r.strValues.Has(ls.Get(r.key))
+	default:
+		return false
+	}
+}
+
+func (sg *LabelSelector) Matches(ls Labels) bool {
+	for _, req := range sg.Requirements {
+		if !req.Matches(ls) {
+			return false
+		}
+	}
+	return true
+}
+
 func try(selectorPiece, op string) (lhs, rhs string, ok bool) {
 	pieces := strings.Split(selectorPiece, op)
 	if len(pieces) == 2 {
diff --git a/pkg/labels/selector_test.go b/pkg/labels/selector_test.go
index 6c5b81296e3..5539d71ea84 100644
--- a/pkg/labels/selector_test.go
+++ b/pkg/labels/selector_test.go
@@ -18,6 +18,8 @@ package labels
 
 import (
 	"testing"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
 )
 
 func TestSelectorParse(t *testing.T) {
@@ -163,3 +165,57 @@ func TestSetIsEmpty(t *testing.T) {
 		t.Errorf("Nested andTerm should not be empty")
 	}
 }
+
+func expectMatchRequirement(t *testing.T, req Requirement, ls Set) {
+	if !req.Matches(ls) {
+		t.Errorf("Wanted '%+v' to match '%s', but it did not.\n", req, ls)
+	}
+}
+
+func expectNoMatchRequirement(t *testing.T, req Requirement, ls Set) {
+	if req.Matches(ls) {
+		t.Errorf("Wanted '%+v' to not match '%s', but it did.", req, ls)
+	}
+}
+
+func TestRequirementMatches(t *testing.T) {
+	s := Set{"x": "foo", "y": "baz"}
+	a := Requirement{key: "x", operator: IN, strValues: util.NewStringSet("foo")}
+	b := Requirement{key: "x", operator: NOT_IN, strValues: util.NewStringSet("beta")}
+	c := Requirement{key: "y", operator: IN, strValues: nil}
+	d := Requirement{key: "y", strValues: util.NewStringSet("foo")}
+	expectMatchRequirement(t, a, s)
+	expectMatchRequirement(t, b, s)
+	expectNoMatchRequirement(t, c, s)
+	expectNoMatchRequirement(t, d, s)
+}
+
+func expectMatchLabSelector(t *testing.T, lsel LabelSelector, s Set) {
+	if !lsel.Matches(s) {
+		t.Errorf("Wanted '%+v' to match '%s', but it did not.\n", lsel, s)
+	}
+}
+
+func expectNoMatchLabSelector(t *testing.T, lsel LabelSelector, s Set) {
+	if lsel.Matches(s) {
+		t.Errorf("Wanted '%+v' to not match '%s', but it did.\n", lsel, s)
+	}
+}
+
+func TestLabelSelectorMatches(t *testing.T) {
+	s := Set{"x": "foo", "y": "baz"}
+	allMatch := LabelSelector{
+		Requirements: []Requirement{
+			{key: "x", operator: IN, strValues: util.NewStringSet("foo")},
+			{key: "y", operator: NOT_IN, strValues: util.NewStringSet("alpha")},
+		},
+	}
+	singleNonMatch := LabelSelector{
+		Requirements: []Requirement{
+			{key: "x", operator: IN, strValues: util.NewStringSet("foo")},
+			{key: "y", operator: IN, strValues: util.NewStringSet("alpha")},
+		},
+	}
+	expectMatchLabSelector(t, allMatch, s)
+	expectNoMatchLabSelector(t, singleNonMatch, s)
+}