Index: test/fragment_cache_test.rb
===================================================================
--- test/fragment_cache_test.rb	(revision 270)
+++ test/fragment_cache_test.rb	(working copy)
@@ -21,6 +21,10 @@
     render :text => "doop!"
   end
 
+  def trees_are_swell?
+    true
+  end
+
   def rescue_action(e)
     raise e
   end
@@ -160,4 +164,26 @@
 
     get :index
   end
+
+  specify "should be able to action cache conditionally when passed something that returns true" do
+    BarController.caches_action :page => { :if => :trees_are_swell? }
+    
+    cache_expects(:set).with('test.host/bar/page', page_content, ActsAsCached.config[:ttl])
+    
+    get :page
+    @response.body.should == page_content
+
+    cache_expects(:read).with('test.host/bar/page', nil).returns(page_content)
+
+    get :page
+  end
+
+  specify "should be able to skip action caching when passed something that returns false" do
+    BarController.caches_action :page => { :if => Proc.new {|c| !c.trees_are_swell?} }
+    
+    cache_expects(:set, 0).with('test.host/bar/page', page_content, ActsAsCached.config[:ttl])
+    
+    get :page
+    @response.body.should == page_content
+  end
 end
Index: lib/acts_as_cached/fragment_cache.rb
===================================================================
--- lib/acts_as_cached/fragment_cache.rb	(revision 270)
+++ lib/acts_as_cached/fragment_cache.rb	(working copy)
@@ -36,6 +36,31 @@
             end
           end
         end
+
+        # override to skip caching/rendering on evaluated if option
+        def before(controller)
+          return unless @actions.include?(controller.action_name.intern)
+          action_cache_path = ActionController::Caching::Actions::ActionCachePath.new(controller)
+          conditional = @actions[controller.action_name.intern][:if]
+
+          # should probably be like ActiveRecord::Validations.evaluate_condition.  color me lazy.
+          if conditional
+            conditional = if conditional.respond_to?("call")
+              conditional.call(controller)
+            elsif controller.send(conditional)
+              true
+            end
+          end
+          @actions.delete(controller.action_name.intern) if conditional == false
+
+          cache = controller.read_fragment(action_cache_path.path)
+          if (cache and (conditional || conditional.nil?))
+            controller.rendered_action_cache = true
+            set_content_type!(action_cache_path)
+            controller.send(:render_text, cache)
+            return false
+          end
+        end
         
         # override to pass along the ttl hash
         def after(controller)