diff --git a/core/src/main/java/io/grpc/Attributes.java b/core/src/main/java/io/grpc/Attributes.java
index 71f0a0cfc4..a338e263c5 100644
--- a/core/src/main/java/io/grpc/Attributes.java
+++ b/core/src/main/java/io/grpc/Attributes.java
@@ -33,7 +33,9 @@ package io.grpc;
 
 import com.google.common.base.Preconditions;
 
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.Set;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
@@ -45,7 +47,7 @@ import javax.annotation.concurrent.Immutable;
 @Immutable
 public final class Attributes {
 
-  private final HashMap<String, Object> data = new HashMap<String, Object>();
+  private final HashMap<Key<?>, Object> data = new HashMap<Key<?>, Object>();
 
   public static final Attributes EMPTY = new Attributes();
 
@@ -58,7 +60,16 @@ public final class Attributes {
   @SuppressWarnings("unchecked")
   @Nullable
   public <T> T get(Key<T> key) {
-    return (T) data.get(key.name);
+    return (T) data.get(key);
+  }
+
+  /**
+   * Returns set of keys stored in container.
+   *
+   * @return Set of Key objects.
+   */
+  public Set<Key<?>> keys() {
+    return Collections.unmodifiableSet(data.keySet());
   }
 
   /**
@@ -71,13 +82,7 @@ public final class Attributes {
   public static final class Key<T> {
     private final String name;
 
-    /**
-     * Construct the key.
-     *
-     * @param name the name, which should be namespaced like com.foo.BarAttribute to avoid
-     *             collision.
-     */
-    public Key(String name) {
+    private Key(String name) {
       this.name = name;
     }
 
@@ -85,6 +90,18 @@ public final class Attributes {
     public String toString() {
       return name;
     }
+
+    /**
+     * Factory method for creating instances of {@link Key}.
+     *
+     * @param name the name of Key, which should be namespaced like com.foo.BarAttribute to avoid
+     *             collision. Name collision, won't cause key collision.
+     * @param <T> Key type
+     * @return Key object
+     */
+    public static <T> Key<T> of(String name) {
+      return new Key<T>(name);
+    }
   }
 
   @Override
@@ -100,7 +117,7 @@ public final class Attributes {
     }
 
     public <T> Builder set(Key<T> key, T value) {
-      product.data.put(key.name, value);
+      product.data.put(key, value);
       return this;
     }
 
diff --git a/core/src/main/java/io/grpc/NameResolver.java b/core/src/main/java/io/grpc/NameResolver.java
index 29db2df9fe..54d7eacf9c 100644
--- a/core/src/main/java/io/grpc/NameResolver.java
+++ b/core/src/main/java/io/grpc/NameResolver.java
@@ -74,7 +74,7 @@ public abstract class NameResolver {
      * port number.
      */
     public static final Attributes.Key<Integer> PARAMS_DEFAULT_PORT =
-        new Attributes.Key<Integer>("io.grpc.NameResolverDefaultPort");
+        Attributes.Key.of("io.grpc.NameResolverDefaultPort");
 
     /**
      * Creates a {@link NameResolver} for the given target URI, or {@code null} if the given URI
diff --git a/core/src/test/java/io/grpc/AttributesTest.java b/core/src/test/java/io/grpc/AttributesTest.java
new file mode 100644
index 0000000000..3f09c5c1c9
--- /dev/null
+++ b/core/src/test/java/io/grpc/AttributesTest.java
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2016, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ *    * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package io.grpc;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link Attributes}. */
+@RunWith(JUnit4.class)
+public class AttributesTest {
+  private static Attributes.Key<String> YOLO_KEY = Attributes.Key.of("yolo");
+
+  @Test
+  public void buildAttributes() {
+    Attributes attrs = Attributes.newBuilder().set(YOLO_KEY, "To be, or not to be?").build();
+    assertSame("To be, or not to be?", attrs.get(YOLO_KEY));
+    assertEquals(1, attrs.keys().size());
+  }
+
+  @Test
+  public void duplicates() {
+    Attributes attrs = Attributes.newBuilder()
+            .set(YOLO_KEY, "To be?")
+            .set(YOLO_KEY, "Or not to be?")
+            .set(Attributes.Key.of("yolo"), "I'm not a duplicate")
+            .build();
+    assertSame("Or not to be?", attrs.get(YOLO_KEY));
+    assertEquals(2, attrs.keys().size());
+  }
+
+  @Test
+  public void empty() {
+    assertEquals(0, Attributes.EMPTY.keys().size());
+  }
+}
diff --git a/core/src/test/java/io/grpc/CallOptionsTest.java b/core/src/test/java/io/grpc/CallOptionsTest.java
index fec6ce8dfc..8c1fa39df7 100644
--- a/core/src/test/java/io/grpc/CallOptionsTest.java
+++ b/core/src/test/java/io/grpc/CallOptionsTest.java
@@ -53,7 +53,7 @@ import java.util.concurrent.TimeUnit;
 public class CallOptionsTest {
   private String sampleAuthority = "authority";
   private Long sampleDeadlineNanoTime = 1L;
-  private Key<String> sampleKey = new Attributes.Key<String>("sample");
+  private Key<String> sampleKey = Attributes.Key.of("sample");
   private Attributes sampleAffinity = Attributes.newBuilder().set(sampleKey, "blah").build();
   private CallOptions allSet = CallOptions.DEFAULT
       .withAuthority(sampleAuthority)