diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 109f2752f62df..9469e5b4885b9 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,5 +1,17 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Added controller-level etag additions that will be part of the action etag computation *Jeremy Kemper/DHH*
+
+      class InvoicesController < ApplicationController
+        etag { current_user.try :id }
+        
+        def show
+          # Etag will differ even for the same invoice when it's viewed by a different current_user
+          @invoice = Invoice.find(params[:id])
+          fresh_when(@invoice)
+        end
+      end
+
 *   Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) *DHH*
 
 *   When building a URL fails, add missing keys provided by Journey. Failed URL
diff --git a/actionpack/lib/action_controller/metal/conditional_get.rb b/actionpack/lib/action_controller/metal/conditional_get.rb
index 2193dde667a95..1445b3e3837b0 100644
--- a/actionpack/lib/action_controller/metal/conditional_get.rb
+++ b/actionpack/lib/action_controller/metal/conditional_get.rb
@@ -5,6 +5,30 @@ module ConditionalGet
     include RackDelegation
     include Head
 
+    included { cattr_accessor(:etaggers) { Array.new } }
+
+    module ClassMethods
+      # Allows you to consider additional controller-wide information when generating an etag.
+      # For example, if you serve pages tailored depending on who's logged in at the moment, you
+      # may want to add the current user id to be part of the etag to prevent authorized displaying
+      # of cached pages.
+      #
+      # === Example
+      #
+      #   class InvoicesController < ApplicationController
+      #     etag { current_user.try :id }
+      #     
+      #     def show
+      #       # Etag will differ even for the same invoice when it's viewed by a different current_user
+      #       @invoice = Invoice.find(params[:id])
+      #       fresh_when(@invoice)
+      #     end
+      #   end
+      def etag(&etagger)
+        self.etaggers += [etagger]
+      end
+    end
+
     # Sets the etag, last_modified, or both on the response and renders a
     # <tt>304 Not Modified</tt> response if the request is already fresh.
     #
@@ -42,12 +66,12 @@ def fresh_when(record_or_options, additional_options = {})
         options.assert_valid_keys(:etag, :last_modified, :public)
       else
         record  = record_or_options
-        options = { :etag => record, :last_modified => record.try(:updated_at) }.merge(additional_options)
+        options = { etag: record, last_modified: record.try(:updated_at) }.merge(additional_options)
       end
 
-      response.etag          = options[:etag]          if options[:etag]
-      response.last_modified = options[:last_modified] if options[:last_modified]
-      response.cache_control[:public] = true if options[:public]
+      response.etag          = combine_etags(options[:etag]) if options[:etag]
+      response.last_modified = options[:last_modified]       if options[:last_modified]
+      response.cache_control[:public] = true                 if options[:public]
 
       head :not_modified if request.fresh?(response)
     end
@@ -133,5 +157,11 @@ def expires_in(seconds, options = {}) #:doc:
     def expires_now #:doc:
       response.cache_control.replace(:no_cache => true)
     end
+    
+    
+    private
+      def combine_etags(etag)
+        [ etag, *etaggers.map { |etagger| instance_exec &etagger }.compact ]
+      end
   end
 end
diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index 3f047fc9b577d..fd8f87e377377 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -22,6 +22,18 @@ def new
   end
 end
 
+class TestControllerWithExtraEtags < ActionController::Base
+  etag { nil  }
+  etag { 'ab' }
+  etag { :cde }
+  etag { [:f] }
+  etag { nil  }
+
+  def fresh
+    render text: "stale" if stale?(etag: '123')
+  end
+end
+
 class TestController < ActionController::Base
   protect_from_forgery
 
@@ -1626,6 +1638,26 @@ def test_last_modified_works_with_less_than_too
   end
 end
 
+class EtagRenderTest < ActionController::TestCase
+  tests TestControllerWithExtraEtags
+
+  def setup
+    super
+    @request.host = "www.nextangle.com"
+  end
+
+  def test_multiple_etags
+    @request.if_none_match = %("#{Digest::MD5.hexdigest(ActiveSupport::Cache.expand_cache_key([ "123", 'ab', :cde, [:f] ]))}")
+    get :fresh
+    assert_response :not_modified
+
+    @request.if_none_match = %("nomatch")
+    get :fresh
+    assert_response :success
+  end
+end
+
+
 class MetalRenderTest < ActionController::TestCase
   tests MetalTestController