diff --git a/activesupport/lib/active_support/core_ext/array/grouping.rb b/activesupport/lib/active_support/core_ext/array/grouping.rb
index f782f8f..97980ff 100644
--- a/activesupport/lib/active_support/core_ext/array/grouping.rb
+++ b/activesupport/lib/active_support/core_ext/array/grouping.rb
@@ -100,6 +100,44 @@ module ActiveSupport #:nodoc:
             results
           end
         end
+
+        # Same as Array#uniq but accepts block argument which result will 
+        # be used for determining which values are unique.
+        #
+        #   a = ['a', 'A', 'bb', 'bB', 'Bb', 'Cc', 'cc']
+        #   a.uniq { |i| i.downcase } # => ["a", "bb", "Cc"]
+        def uniq_with_block(&block)
+          if block
+            first_values = {}
+            map do |value|
+              key = yield value
+              first_values[key] ||= value
+              first_values[key]
+            end.uniq
+          else
+            uniq_without_block
+          end
+        end
+
+        # Adds block support to Array#uniq!
+        def uniq_with_block!(&block)
+          if block
+            replace uniq_with_block(&block)
+          else
+            uniq_without_block!
+          end
+        end
+
+        # This is evil and it's only because of my lack of knowledge I guess.
+        def self.append_features(mod)
+          super(mod)
+          mod.instance_eval do
+            alias_method :uniq_without_block, :uniq
+            alias_method :uniq, :uniq_with_block
+            alias_method :uniq_without_block!, :uniq!
+            alias_method :uniq!, :uniq_with_block!
+          end
+        end
       end
     end
   end
diff --git a/activesupport/test/core_ext/array_ext_test.rb b/activesupport/test/core_ext/array_ext_test.rb
index 93f4482..9e6f271 100644
--- a/activesupport/test/core_ext/array_ext_test.rb
+++ b/activesupport/test/core_ext/array_ext_test.rb
@@ -176,6 +176,33 @@ class ArrayExtGroupingTests < Test::Unit::TestCase
     assert_equal [[1, 2, 3], [4, 5], [6, 7]],
       (1..7).to_a.in_groups(3, false)
   end
+
+  def test_uniq_with_downcase
+    assert_equal %w{aa Bb cc},
+      %w{aa aA Aa Bb bb bB cc Cc}.uniq { |e| e.downcase }
+  end
+
+  def test_uniq_with_lame_block
+    a = %w{a b c d aa a b c d bb}
+    assert_equal a.uniq, a.uniq { |e| e }
+  end
+
+  def test_uniq_with_empty_array
+    assert_equal [], [].uniq { |e| e }
+  end
+
+  def test_uniq_destructive
+    source = %w{aa Aa bb}
+    source.uniq! { |e| e.downcase }
+    assert_equal %w{aa bb}, source
+  end
+  
+  def test_uniq_destructive_without_block
+    source = %w{aa Aa bb aa bb}
+    source2 = 
+    source.uniq!
+    assert_equal %w{aa Aa bb}, source
+  end
 end
 
 class ArraySplitTests < Test::Unit::TestCase