Using this simple script, I expected that a None should be returned (according to http://www.zope.org/Documentation/Books/ZopeBook/2_6Edition/Sessions.stx): data = context.session_data_manager.getSessionData( create=0 ) data.invalidate() return str( data ) # str() just to see None But a result like this is allways returned: id: 10360120480192202025, token: 54001646A0iEAi2X9io, contents: [] with id change at each call (token is the same because the browser is the same). A new session is ceated at each hit (refresh) in the same browser: and the counter in the transient object container is increased accordingly. I did put Data object timeout value in minutes = 1, but after 30 minuts a new hit increase the counter. Does create=0 work properly? Does invalidate() work at all? What am I doing wrong? Thanks for help. p.t.