diff --git a/lib/gitmodel.rb b/lib/gitmodel.rb
index 57fedeb..afcaf87 100644
--- a/lib/gitmodel.rb
+++ b/lib/gitmodel.rb
@@ -16,9 +16,12 @@
 require 'gitmodel/index'
 require 'gitmodel/persistable'
 require 'gitmodel/transaction'
+require 'gitmodel/serialization/yajl'
+require 'gitmodel/serialization/yaml'
 
 module GitModel
 
+  DEFAULT_SERIALIZER = GitModel::Serialization::Yajl
   # db_root must be an existing git repo. (It can be created with create_db!)
   # Bare repositories aren't supported yet, it must be a normal git repo with a
   # working directory and a '.git' subdirectory.
@@ -38,6 +41,9 @@ module GitModel
   mattr_accessor :memcache_servers
   mattr_accessor :memcache_namespace
 
+  mattr_accessor :serializer
+  self.serializer = DEFAULT_SERIALIZER
+
   def self.repo
     @@repo = Grit::Repo.new(GitModel.db_root)
   end
@@ -122,4 +128,13 @@ def self.head_sha(branch_name)
     ref = File.join(repo.git.git_dir, "refs/heads/#{branch_name}")
     File.exist?(ref) ? File.read(ref).chomp : nil
   end
+  
+  def self.attributes_filename
+    serializer.attributes_filename
+  end
+  
+  def self.filename_extension
+    serializer.filename_extension
+  end
+  
 end
diff --git a/lib/gitmodel/index.rb b/lib/gitmodel/index.rb
index 485608c..8e6e147 100644
--- a/lib/gitmodel/index.rb
+++ b/lib/gitmodel/index.rb
@@ -27,7 +27,7 @@ def attr_index(attr)
     end
 
     def filename
-      File.join(@model_class.db_subdir, '_indexes.json')
+      File.join(@model_class.db_subdir, "_indexes.#{GitModel.filename_extension}")
     end
 
     def generated?(branch = GitModel.default_branch)
@@ -48,7 +48,7 @@ def save(options = {})
           end
           data << [attr,values_and_ids]
         end
-        data = Yajl::Encoder.encode(data, nil, :pretty => true)
+        data = GitModel.serializer.encode(data)
         t.index.add(filename, data)
       end
     end
diff --git a/lib/gitmodel/persistable.rb b/lib/gitmodel/persistable.rb
index ed03436..c11e62a 100644
--- a/lib/gitmodel/persistable.rb
+++ b/lib/gitmodel/persistable.rb
@@ -124,7 +124,7 @@ def save(options = {})
         transaction = options.delete(:transaction) || GitModel::Transaction.new(options) 
         result = transaction.execute do |t|
           # Write the attributes to the attributes file
-          t.index.add(File.join(dir, 'attributes.json'), Yajl::Encoder.encode(attributes, nil, :pretty => true))
+          t.index.add(File.join(dir, 'attributes.json'), GitModel.serializer.encode(attributes))
 
           # Write the blob files
           blobs.each do |name, data|
diff --git a/lib/gitmodel/serialization/yajl.rb b/lib/gitmodel/serialization/yajl.rb
new file mode 100644
index 0000000..0d14a4b
--- /dev/null
+++ b/lib/gitmodel/serialization/yajl.rb
@@ -0,0 +1,19 @@
+module GitModel
+  module Serialization
+    class Yajl
+      class << self
+        def filename_extension
+          "json"
+        end
+        
+        def attributes_filename
+          "attributes.#{filename_extension}"
+        end
+        
+        def encode(data)
+          ::Yajl::Encoder.encode(data, nil, :pretty => true)
+        end
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/lib/gitmodel/serialization/yaml.rb b/lib/gitmodel/serialization/yaml.rb
new file mode 100644
index 0000000..551a367
--- /dev/null
+++ b/lib/gitmodel/serialization/yaml.rb
@@ -0,0 +1,19 @@
+module GitModel
+  module Serialization
+    class Yaml
+      class << self
+        def filename_extension
+          "yaml"
+        end
+        
+        def attributes_filename
+          "attributes.#{filename_extension}"
+        end
+        
+        def encode(data)
+          data.to_hash.to_yaml
+        end
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/spec/gitmodel/index_spec.rb b/spec/gitmodel/index_spec.rb
index 5fea8cd..353bd62 100644
--- a/spec/gitmodel/index_spec.rb
+++ b/spec/gitmodel/index_spec.rb
@@ -27,10 +27,22 @@
     @i.attr_index(:x).should == {1 => SortedSet.new(["foo", "bar"]), 2 => SortedSet.new(["baz"])}
   end
 
-  it "knows it's filename" do
-    @i.filename.should == "test_entities/_indexes.json"
-  end
+  context "with serializer" do
+    context "Yajl" do
+      it "knows it's filename" do
+        GitModel.serializer = GitModel::Serialization::Yajl
+        @i.filename.should == "test_entities/_indexes.json"
+      end
+    end
 
+    context "Yaml" do
+      it "knows it's filename" do
+        GitModel.serializer = GitModel::Serialization::Yaml
+        @i.filename.should == "test_entities/_indexes.yaml"
+      end
+    end
+  end
+  
   it "can save itself to a JSON file" do
     @i.save
     json = <<-END.strip
diff --git a/spec/gitmodel/serialization/yajl_spec.rb b/spec/gitmodel/serialization/yajl_spec.rb
new file mode 100644
index 0000000..2cb1219
--- /dev/null
+++ b/spec/gitmodel/serialization/yajl_spec.rb
@@ -0,0 +1,43 @@
+require 'spec_helper'
+
+RSpec.configure do |c|
+  c.include RawData
+end
+
+describe GitModel::Serialization::Yajl do
+  describe ".encode" do    
+    it "should encode data as json" do
+      data = {
+        x: 1,
+        y: "bob",
+        z: [4,5,6]
+      }
+      GitModel::Serialization::Yajl.encode(data).should ==
+        ::Yajl::Encoder.encode(data, nil, :pretty => true)
+    end
+  end
+  
+  context "set as GitModel serializer" do
+    before do
+      GitModel.serializer = GitModel::Serialization::Yajl
+    end
+  
+  
+    it "should use attributes.json as the attribute filename" do    
+      GitModel.attributes_filename.should == "attributes.json"
+    end
+    
+    it "should save attributes as json" do
+      data = {
+        x: 1,
+        y: "bob",
+        z: [4,5,6]
+      }
+    
+      TestEntity.create!(:id => "foo", 
+        :attributes => {:x => 1, :y => "bob", :z => [4,5,6]})
+    
+      last_saved_entity_attributes('foo').should == Yajl::Encoder.encode(data, nil, :pretty => true)
+    end
+  end
+end
\ No newline at end of file
diff --git a/spec/gitmodel/serialization/yaml_spec.rb b/spec/gitmodel/serialization/yaml_spec.rb
new file mode 100644
index 0000000..dba238c
--- /dev/null
+++ b/spec/gitmodel/serialization/yaml_spec.rb
@@ -0,0 +1,44 @@
+require 'spec_helper'
+
+RSpec.configure do |c|
+  c.include RawData
+end
+
+describe GitModel::Serialization::Yaml do
+  describe ".encode" do    
+    it "should encode data as yaml" do
+      data = {
+        x: 1,
+        y: "bob",
+        z: [4,5,6]
+      }
+      GitModel::Serialization::Yaml.encode(data).should ==
+        data.to_yaml
+    end
+  end
+  
+  context "set as GitModel serializer" do
+    before do
+      GitModel.serializer = GitModel::Serialization::Yaml
+    end
+  
+  
+    it "should use attributes.json as the attribute filename" do    
+      GitModel.attributes_filename.should == "attributes.yaml"
+    end
+    
+    
+    it "should save attributes as yaml" do
+      data = {
+        'x' => 1,
+        'y' => "bob",
+        'z' => [4,5,6]
+      }
+    
+      TestEntity.create!(:id => "foo", 
+        :attributes => {:x => 1, :y => "bob", :z => [4,5,6]})
+    
+      last_saved_entity_attributes('foo').should == data.to_yaml
+    end
+  end
+end
\ No newline at end of file
diff --git a/spec/gitmodel_spec.rb b/spec/gitmodel_spec.rb
index 69bfcc2..1183d3d 100644
--- a/spec/gitmodel_spec.rb
+++ b/spec/gitmodel_spec.rb
@@ -44,5 +44,10 @@
     end
   end
 
+  describe ".serializer" do
+    it "should be Yajl by default" do
+      GitModel.serializer.should == GitModel::Serialization::Yajl
+    end
+  end
 end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 51a1f51..3001488 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -8,6 +8,10 @@
 
 RSpec.configure do |c|
   c.mock_with :rspec
+  
+  c.before(:each) do
+    GitModel.serializer = GitModel::DEFAULT_SERIALIZER
+  end
 end
 
 class TestEntity
@@ -19,3 +23,10 @@ class TestEntity2
 
 #GitModel.logger.level = ::Logger::DEBUG
 GitModel.memcache_servers = ['localhost']
+
+module RawData
+  def last_saved_entity_attributes(id)
+    repo = Grit::Repo.new(GitModel.db_root)
+    (repo.commits.first.tree / File.join(TestEntity.db_subdir, id, 'attributes.json')).data
+  end
+end
\ No newline at end of file