after having some weird issues with Sessions and ZEO usage I've found out part of the problem. It turns out certain browsers (IE6 mostly) save the session ID cookies, but sometimes these disappear. This results in a new _ZopeId being generated and thus the new session is empty. At first i thought it was a session product problem, but in recreating this with my own session management (mysql based) the same issue arises. I don't know why this happens, the only obstacle I'm facing now is to create an adequate solution ;) Because the cookie method is not flawless we've decided to create a way to uniquely determine a user without using a client side cookie, we are already using the IP address for this, Of course that is not enough, so I was wondering what other 'unique' elements could be used for this. I've thought about adding user agent, but this is to general I think. Internal IP would be ideal, but I'm not sure this can be done (probably not). Maybe there are also 'other' zope session products that work in another way and might fix my problems as a whole?