diff --git a/test/testcases.js b/test/testcases.js
index 35a25dbb..57c4de63 100644
--- a/test/testcases.js
+++ b/test/testcases.js
@@ -22,6 +22,7 @@ var tests = [
   'auto-test-iterations-basic.html',
   'auto-test-iterations-fill.html',
   'auto-test-keyframe-creation.html',
+  'auto-test-keyframe-easing.html',
   'auto-test-length-units.html',
   'auto-test-matrix-transforms.html',
   'auto-test-non-numeric.html',
diff --git a/test/testcases/auto-test-keyframe-easing-checks.js b/test/testcases/auto-test-keyframe-easing-checks.js
new file mode 100644
index 00000000..c1fc1db4
--- /dev/null
+++ b/test/testcases/auto-test-keyframe-easing-checks.js
@@ -0,0 +1,65 @@
+timing_test(function() {
+  at(0, function() {
+    assert_styles("#target",{'height':'0px'});
+  });
+  at(0.25, function() {
+    assert_styles("#target",{'height':'12.5px'});
+  });
+  at(0.5, function() {
+    assert_styles("#target",{'height':'25px'});
+  });
+  at(0.75, function() {
+    assert_styles("#target",{'height':'37.5px'});
+  });
+  at(1, function() {
+    assert_styles("#target",{'height':'50px'});
+  });
+  at(1.25, function() {
+    assert_styles("#target",{'height':'62.5px'});
+  });
+  at(1.5, function() {
+    assert_styles("#target",{'height':'75px'});
+  });
+  at(1.75, function() {
+    assert_styles("#target",{'height':'87.5px'});
+  });
+  at(2, function() {
+    assert_styles("#target",{'height':'100px'});
+  });
+  at(2.25, function() {
+    assert_styles("#target",{'height':'106.5px'});
+  });
+  at(2.5, function() {
+    assert_styles("#target",{'height':'125px'});
+  });
+  at(2.75, function() {
+    assert_styles("#target",{'height':'143.5px'});
+  });
+  at(3, function() {
+    assert_styles("#target",{'height':'150px'});
+  });
+  at(3.25, function() {
+    assert_styles("#target",{'height':'150px'});
+  });
+  at(3.5, function() {
+    assert_styles("#target",{'height':'150px'});
+  });
+  at(3.75, function() {
+    assert_styles("#target",{'height':'200px'});
+  });
+  at(4, function() {
+    assert_styles("#target",{'height':'200px'});
+  });
+  at(4.25, function() {
+    assert_styles("#target",{'height':'200px'});
+  });
+  at(4.5, function() {
+    assert_styles("#target",{'height':'225px'});
+  });
+  at(4.75, function() {
+    assert_styles("#target",{'height':'225px'});
+  });
+  at(5, function() {
+    assert_styles("#target",{'height':'250px'});
+  });
+}, "Auto generated tests");
diff --git a/test/testcases/auto-test-keyframe-easing.html b/test/testcases/auto-test-keyframe-easing.html
new file mode 100644
index 00000000..f13bd015
--- /dev/null
+++ b/test/testcases/auto-test-keyframe-easing.html
@@ -0,0 +1,64 @@
+<style>
+#container {
+  position: relative;
+}
+
+#control {
+  position: absolute;
+  background-color: black;
+  width: 20px;
+  height: 0px;
+}
+
+#target {
+  position: absolute;
+  left: 20px;
+  background-color: rgba(0, 128, 0, 0.25);
+  width: 280px;
+  height: 0px;
+}
+
+.block {
+  padding-left: 30px;
+  border-bottom: 1px solid black;
+  box-sizing: border-box;
+  width: 300px;
+  height: 50px;
+  font-size: 20px;
+}
+</style>
+
+<div id="container">
+  <div id="control"></div>
+  <div id="target"></div>
+</div>
+<script src="../bootstrap.js"></script>
+<script>
+var easings = [
+  '',
+  'linear',
+  'ease-in-out',
+  'step-middle',
+  'steps(4, end)',
+];
+
+var keyframeHeight = 50;
+var timing = {duration: easings.length, fill: 'forwards'};
+
+control.animate({height: easings.length * keyframeHeight + 'px'}, timing);
+
+var keyframes = [];
+easings.forEach(function (easing, i) {
+  var textBlock = document.createElement('div');
+  textBlock.textContent = easing.length ? easing : '<default>';
+  textBlock.classList.add('block');
+  container.appendChild(textBlock);
+  var keyframe = {height: i * keyframeHeight + 'px'};
+  if (easing.length) {
+    keyframe.easing = easing;
+  }
+  keyframes.push(keyframe);
+});
+keyframes.push({height: easings.length * keyframeHeight + 'px'});
+target.animate(keyframes, timing);
+</script>
diff --git a/web-animations.js b/web-animations.js
index 46235590..7fc49fb3 100644
--- a/web-animations.js
+++ b/web-animations.js
@@ -2006,7 +2006,8 @@ var expandShorthand = function(property, value, result) {
 var normalizeKeyframeDictionary = function(properties) {
   var result = {
     offset: null,
-    composite: null
+    composite: null,
+    easing: presetTimingFunctions.linear
   };
   var animationProperties = [];
   for (var property in properties) {
@@ -2020,6 +2021,8 @@ var normalizeKeyframeDictionary = function(properties) {
           properties.composite === 'replace') {
         result.composite = properties.composite;
       }
+    } else if (property === 'easing') {
+      result.easing = TimingFunction.createFromString(properties.easing);
     } else {
       // TODO: Check whether this is a supported property.
       animationProperties.push(property);
@@ -2186,6 +2189,9 @@ KeyframeEffect.prototype = createObject(AnimationEffect.prototype, {
     }
     var intervalDistance = (timeFraction - startKeyframe.offset) /
         (endKeyframe.offset - startKeyframe.offset);
+    if (startKeyframe.easing) {
+      intervalDistance = startKeyframe.easing.scaleTime(intervalDistance);
+    }
     return new BlendedCompositableValue(
         new AddReplaceCompositableValue(startKeyframe.rawValue(),
             this._compositeForKeyframe(startKeyframe)),
@@ -2207,8 +2213,8 @@ KeyframeEffect.prototype = createObject(AnimationEffect.prototype, {
         }
         var frame = distributedFrames[i];
         this._cachedPropertySpecificKeyframes[property].push(
-            new PropertySpecificKeyframe(frame.offset,
-                frame.composite, property, frame.cssValues[property]));
+            new PropertySpecificKeyframe(frame.offset, frame.composite,
+                frame.easing, property, frame.cssValues[property]));
       }
     }
 
@@ -2221,12 +2227,12 @@ KeyframeEffect.prototype = createObject(AnimationEffect.prototype, {
       // Add synthetic keyframes at offsets of 0 and 1 if required.
       if (frames[0].offset !== 0.0) {
         var keyframe = new PropertySpecificKeyframe(0.0, 'add',
-            property, cssNeutralValue);
+            presetTimingFunctions.linear, property, cssNeutralValue);
         frames.unshift(keyframe);
       }
       if (frames[frames.length - 1].offset !== 1.0) {
         var keyframe = new PropertySpecificKeyframe(1.0, 'add',
-            property, cssNeutralValue);
+            presetTimingFunctions.linear, property, cssNeutralValue);
         frames.push(keyframe);
       }
       ASSERT_ENABLED && assert(
@@ -2372,7 +2378,7 @@ KeyframeEffect.prototype = createObject(AnimationEffect.prototype, {
  *
  * @constructor
  */
-var KeyframeInternal = function(offset, composite) {
+var KeyframeInternal = function(offset, composite, easing) {
   ASSERT_ENABLED && assert(
       typeof offset === 'number' || offset === null,
       'Invalid offset value');
@@ -2381,6 +2387,7 @@ var KeyframeInternal = function(offset, composite) {
       'Invalid composite value');
   this.offset = offset;
   this.composite = composite;
+  this.easing = easing;
   this.cssValues = {};
 };
 
@@ -2405,9 +2412,12 @@ KeyframeInternal.createFromNormalizedProperties = function(properties) {
   ASSERT_ENABLED && assert(
       isDefinedAndNotNull(properties) && typeof properties === 'object',
       'Properties must be an object');
-  var keyframe = new KeyframeInternal(properties.offset, properties.composite);
+  var keyframe = new KeyframeInternal(properties.offset, properties.composite,
+      properties.easing);
   for (var candidate in properties) {
-    if (candidate !== 'offset' && candidate !== 'composite') {
+    if (candidate !== 'offset' &&
+        candidate !== 'composite' &&
+        candidate !== 'easing') {
       keyframe.addPropertyValuePair(candidate, properties[candidate]);
     }
   }
@@ -2417,9 +2427,11 @@ KeyframeInternal.createFromNormalizedProperties = function(properties) {
 
 
 /** @constructor */
-var PropertySpecificKeyframe = function(offset, composite, property, cssValue) {
+var PropertySpecificKeyframe = function(offset, composite, easing, property,
+    cssValue) {
   this.offset = offset;
   this.composite = composite;
+  this.easing = easing;
   this.property = property;
   this.cssValue = cssValue;
   // Calculated lazily