diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/CommitJsonData.java b/gitiles-servlet/src/main/java/com/google/gitiles/CommitJsonData.java
index 39d9be4..20cb9cd 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/CommitJsonData.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/CommitJsonData.java
@@ -33,10 +33,16 @@
 import javax.annotation.Nullable;
 import javax.servlet.http.HttpServletRequest;
 
-class CommitJsonData {
+public class CommitJsonData {
   static final ImmutableSet<Field> DEFAULT_FIELDS = Sets.immutableEnumSet(
       Field.SHA, Field.TREE, Field.PARENTS, Field.AUTHOR, Field.COMMITTER, Field.MESSAGE);
 
+  public static class Ident {
+    public String name;
+    public String email;
+    public String time;
+  }
+
   static class Commit {
     String commit;
     String tree;
@@ -48,12 +54,6 @@
     List<Diff> treeDiff;
   }
 
-  static class Ident {
-    String name;
-    String email;
-    String time;
-  }
-
   /** @see DiffEntry */
   static class Diff {
     String type;
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/blame/BlameServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/blame/BlameServlet.java
index 04e86a8..f59ba04 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/blame/BlameServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/blame/BlameServlet.java
@@ -31,6 +31,8 @@
 import com.google.gitiles.GitilesView;
 import com.google.gitiles.Renderer;
 import com.google.gitiles.ViewFilter;
+import com.google.gson.GsonBuilder;
+import com.google.gson.reflect.TypeToken;
 import com.google.template.soy.data.SoyListData;
 import com.google.template.soy.data.SoyMapData;
 
@@ -75,43 +77,21 @@
     RevWalk rw = new RevWalk(repo);
     try {
       GitilesAccess access = getAccess(req);
-      RevCommit currCommit = rw.parseCommit(view.getRevision().getId());
-      ObjectId currCommitBlobId = resolveBlob(view, rw, currCommit);
-      if (currCommitBlobId == null) {
-        res.setStatus(SC_NOT_FOUND);
+      RegionResult result = getRegions(view, access, repo, rw, res);
+      if (result == null) {
         return;
       }
 
-      ObjectId lastCommit = cache.findLastCommit(repo, currCommit, view.getPathPart());
-      ObjectId lastCommitBlobId = resolveBlob(view, rw, lastCommit);
-
-      if (!Objects.equal(currCommitBlobId, lastCommitBlobId)) {
-        log.warn(String.format("Blob %s in last modified commit %s for repo %s starting from %s"
-            + " does not match original blob %s",
-            ObjectId.toString(lastCommitBlobId),
-            ObjectId.toString(lastCommit),
-            access.getRepositoryName(),
-            ObjectId.toString(currCommit),
-            ObjectId.toString(currCommitBlobId)));
-        lastCommitBlobId = currCommitBlobId;
-        lastCommit = currCommit;
-      }
-
       String title = "Blame - " + view.getPathPart();
       Map<String, ?> blobData = new BlobSoyData(rw.getObjectReader(), view)
-          .toSoyData(view.getPathPart(), lastCommitBlobId);
+          .toSoyData(view.getPathPart(), result.blobId);
       if (blobData.get("lines") != null) {
-        List<Region> regions = cache.get(repo, lastCommit, view.getPathPart());
-        if (regions.isEmpty()) {
-          res.setStatus(SC_NOT_FOUND);
-          return;
-        }
         DateFormatter df = new DateFormatter(access, Format.ISO);
         renderHtml(req, res, "gitiles.blameDetail", ImmutableMap.of(
             "title", title,
             "breadcrumbs", view.getBreadcrumbs(),
             "data", blobData,
-            "regions", toSoyData(view, rw.getObjectReader(), regions, df)));
+            "regions", toSoyData(view, rw.getObjectReader(), result.regions, df)));
       } else {
         renderHtml(req, res, "gitiles.blameDetail", ImmutableMap.of(
             "title", title,
@@ -123,6 +103,80 @@
     }
   }
 
+  @Override
+  protected void doGetJson(HttpServletRequest req, HttpServletResponse res) throws IOException {
+    GitilesView view = ViewFilter.getView(req);
+    Repository repo = ServletUtils.getRepository(req);
+
+    RevWalk rw = new RevWalk(repo);
+    try {
+      RegionResult result = getRegions(view, getAccess(req), repo, rw, res);
+      if (result == null) {
+        return;
+      }
+      // Output from BlameCache is 0-based for lines. We convert to 1-based for
+      // JSON output later (in RegionAdapter); here we're just filling in the
+      // transient fields.
+      int start = 0;
+      for (Region r : result.regions) {
+        r.setStart(start);
+        start += r.getCount();
+      }
+      renderJson(req, res, ImmutableMap.of("regions", result.regions),
+          new TypeToken<Map<String, List<Region>>>() {}.getType());
+    } finally {
+      rw.release();
+    }
+  }
+
+  @Override
+  protected GsonBuilder newGsonBuilder(HttpServletRequest req) throws IOException {
+    return super.newGsonBuilder(req).registerTypeAdapter(Region.class,
+        new RegionAdapter(new DateFormatter(getAccess(req), Format.ISO)));
+  }
+
+  private static class RegionResult {
+    private final List<Region> regions;
+    private final ObjectId blobId;
+
+    private RegionResult(List<Region> regions, ObjectId blobId) {
+      this.regions = regions;
+      this.blobId = blobId;
+    }
+  }
+
+  private RegionResult getRegions(GitilesView view, GitilesAccess access, Repository repo,
+      RevWalk rw, HttpServletResponse res) throws IOException {
+    RevCommit currCommit = rw.parseCommit(view.getRevision().getId());
+    ObjectId currCommitBlobId = resolveBlob(view, rw, currCommit);
+    if (currCommitBlobId == null) {
+      res.setStatus(SC_NOT_FOUND);
+      return null;
+    }
+
+    ObjectId lastCommit = cache.findLastCommit(repo, currCommit, view.getPathPart());
+    ObjectId lastCommitBlobId = resolveBlob(view, rw, lastCommit);
+
+    if (!Objects.equal(currCommitBlobId, lastCommitBlobId)) {
+      log.warn(String.format("Blob %s in last modified commit %s for repo %s starting from %s"
+          + " does not match original blob %s",
+          ObjectId.toString(lastCommitBlobId),
+          ObjectId.toString(lastCommit),
+          access.getRepositoryName(),
+          ObjectId.toString(currCommit),
+          ObjectId.toString(currCommitBlobId)));
+      lastCommitBlobId = currCommitBlobId;
+      lastCommit = currCommit;
+    }
+
+    List<Region> regions = cache.get(repo, lastCommit, view.getPathPart());
+    if (regions.isEmpty()) {
+      res.setStatus(SC_NOT_FOUND);
+      return null;
+    }
+    return new RegionResult(regions, lastCommitBlobId);
+  }
+
   private static ObjectId resolveBlob(GitilesView view, RevWalk rw, ObjectId commitId)
       throws IOException {
     try {
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/blame/Region.java b/gitiles-servlet/src/main/java/com/google/gitiles/blame/Region.java
index 13a3dd3..09a39d6 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/blame/Region.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/blame/Region.java
@@ -42,6 +42,10 @@
     this.count = end - start;
   }
 
+  void setStart(int start) {
+    this.start = start;
+  }
+
   int getStart() {
     return start;
   }
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/blame/RegionAdapter.java b/gitiles-servlet/src/main/java/com/google/gitiles/blame/RegionAdapter.java
new file mode 100644
index 0000000..a9710ae
--- /dev/null
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/blame/RegionAdapter.java
@@ -0,0 +1,55 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// 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 com.google.gitiles.blame;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.gitiles.DateFormatter;
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
+import org.eclipse.jgit.lib.ObjectId;
+
+import java.io.IOException;
+
+class RegionAdapter extends TypeAdapter<Region> {
+  private final DateFormatter df;
+
+  RegionAdapter(DateFormatter df) {
+    this.df = checkNotNull(df, "DateFormatter");
+  }
+
+  @Override
+  public void write(JsonWriter out, Region value) throws IOException {
+    out.beginObject()
+        .name("start").value(value.getStart() + 1)
+        .name("count").value(value.getCount())
+        .name("path").value(value.getSourcePath())
+        .name("commit").value(ObjectId.toString(value.getSourceCommit()))
+        .name("author").beginObject()
+        // TODO(dborowitz): Use an adapter from CommitJsonData instead.
+        .name("name").value(value.getSourceAuthor().getName())
+        .name("email").value(value.getSourceAuthor().getEmailAddress())
+        .name("time").value(df.format(value.getSourceAuthor()))
+        .endObject()
+        .endObject();
+  }
+
+  @Override
+  public Region read(JsonReader in) throws IOException {
+    throw new UnsupportedOperationException();
+  }
+}
diff --git a/gitiles-servlet/src/test/java/com/google/gitiles/blame/BlameServletTest.java b/gitiles-servlet/src/test/java/com/google/gitiles/blame/BlameServletTest.java
new file mode 100644
index 0000000..19229e9
--- /dev/null
+++ b/gitiles-servlet/src/test/java/com/google/gitiles/blame/BlameServletTest.java
@@ -0,0 +1,103 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// 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 com.google.gitiles.blame;
+
+import static org.junit.Assert.assertEquals;
+
+import com.google.common.collect.Iterables;
+import com.google.gitiles.CommitJsonData.Ident;
+import com.google.gitiles.FakeHttpServletRequest;
+import com.google.gitiles.FakeHttpServletResponse;
+import com.google.gitiles.GitilesServlet;
+import com.google.gitiles.TestGitilesServlet;
+import com.google.gson.Gson;
+import com.google.gson.reflect.TypeToken;
+
+import org.eclipse.jgit.internal.storage.dfs.DfsRepository;
+import org.eclipse.jgit.internal.storage.dfs.DfsRepositoryDescription;
+import org.eclipse.jgit.internal.storage.dfs.InMemoryRepository;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Map;
+
+public class BlameServletTest {
+  private static class RegionJsonData {
+    int start;
+    int count;
+    String path;
+    String commit;
+    Ident author;
+  }
+
+  private TestRepository<DfsRepository> repo;
+  private GitilesServlet servlet;
+
+  @Before
+  public void setUp() throws Exception {
+    DfsRepository r = new InMemoryRepository(new DfsRepositoryDescription("test"));
+    repo = new TestRepository<DfsRepository>(r);
+    servlet = TestGitilesServlet.create(repo);
+  }
+
+  @Test
+  public void blameJson() throws Exception {
+    String contents1 = "foo\n";
+    String contents2 = "foo\ncontents\n";
+    RevCommit c1 = repo.update("master", repo.commit().add("foo", contents1));
+    RevCommit c2 = repo.update("master", repo.commit().tick(10).parent(c1).add("foo", contents2));
+
+    Map<String, List<RegionJsonData>> result = getBlameJson("/test/+blame/" + c2.name() + "/foo");
+    assertEquals("regions", Iterables.getOnlyElement(result.keySet()));
+    List<RegionJsonData> regions = result.get("regions");
+    assertEquals(2, regions.size());
+
+    RegionJsonData r1 = regions.get(0);
+    assertEquals(1, r1.start);
+    assertEquals(1, r1.count);
+    assertEquals("foo", r1.path);
+    assertEquals(c1.name(), r1.commit);
+    assertEquals("J. Author", r1.author.name);
+    assertEquals("jauthor@example.com", r1.author.email);
+    assertEquals("2009-03-13 17:29:48 -0330", r1.author.time);
+
+    RegionJsonData r2 = regions.get(1);
+    assertEquals(2, r2.start);
+    assertEquals(1, r2.count);
+    assertEquals("foo", r2.path);
+    assertEquals(c2.name(), r2.commit);
+    assertEquals("J. Author", r2.author.name);
+    assertEquals("jauthor@example.com", r2.author.email);
+    assertEquals("2009-03-13 17:29:58 -0330", r2.author.time);
+  }
+
+  private Map<String, List<RegionJsonData>> getBlameJson(String path) throws Exception {
+    FakeHttpServletRequest req = FakeHttpServletRequest.newRequest();
+    req.setPathInfo(path);
+    req.setQueryString("format=JSON");
+
+    FakeHttpServletResponse res = new FakeHttpServletResponse();
+    servlet.service(req, res);
+    assertEquals(200, res.getStatus());
+    String body = res.getActualBodyString();
+    String magic = ")]}'\n";
+    assertEquals(magic, body.substring(0, magic.length()));
+    return new Gson().fromJson(body.substring(magic.length()),
+        new TypeToken<Map<String, List<RegionJsonData>>>() {}.getType());
+  }
+}