diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index 186b531ffb..ddf4ce4058 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -409,6 +409,17 @@ module ActiveRecord
         end
 
         def method_missing(method, *args)
+          case method.to_s
+          when 'find_or_create'
+            return find(:first, :conditions => args.first) || create(args.first)
+          when /^find_or_create_by_(.*)$/
+            rest = $1
+            return  send("find_by_#{rest}", *args) ||
+                    method_missing("create_by_#{rest}", *args)
+          when /^create_by_(.*)$/
+            return create Hash[$1.split('_and_').zip(args)]
+          end
+
           if @target.respond_to?(method) || (!@reflection.klass.respond_to?(method) && Class.respond_to?(method))
             if block_given?
               super { |*block_args| yield(*block_args) }
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 45c7498013..5e3ba778f3 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -21,6 +21,68 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     Client.destroyed_client_ids.clear
   end
 
+  def test_create_by
+    person = Person.create! :first_name => 'tenderlove'
+    post   = Post.find :first
+
+    assert_equal [], person.readers
+    assert_nil person.readers.find_by_post_id post.id
+
+    reader = person.readers.create_by_post_id post.id
+
+    assert_equal 1, person.readers.count
+    assert_equal 1, person.readers.length
+    assert_equal post, person.readers.first.post
+    assert_equal person, person.readers.first.person
+  end
+
+  def test_create_by_multi
+    person = Person.create! :first_name => 'tenderlove'
+    post   = Post.find :first
+
+    assert_equal [], person.readers
+
+    reader = person.readers.create_by_post_id_and_skimmer post.id, false
+
+    assert_equal 1, person.readers.count
+    assert_equal 1, person.readers.length
+    assert_equal post, person.readers.first.post
+    assert_equal person, person.readers.first.person
+  end
+
+  def test_find_or_create_by
+    person = Person.create! :first_name => 'tenderlove'
+    post   = Post.find :first
+
+    assert_equal [], person.readers
+    assert_nil person.readers.find_by_post_id post.id
+
+    reader = person.readers.find_or_create_by_post_id post.id
+
+    assert_equal 1, person.readers.count
+    assert_equal 1, person.readers.length
+    assert_equal post, person.readers.first.post
+    assert_equal person, person.readers.first.person
+  end
+
+  def test_find_or_create
+    person = Person.create! :first_name => 'tenderlove'
+    post   = Post.find :first
+
+    assert_equal [], person.readers
+    assert_nil person.readers.find(:first, :conditions => {
+      :post_id => post.id
+    })
+
+    reader = person.readers.find_or_create :post_id => post.id
+
+    assert_equal 1, person.readers.count
+    assert_equal 1, person.readers.length
+    assert_equal post, person.readers.first.post
+    assert_equal person, person.readers.first.person
+  end
+
+
   def force_signal37_to_load_all_clients_of_firm
     companies(:first_firm).clients_of_firm.each {|f| }
   end