Hi Dominic! I applied all steps tat you recomended. Two company users can see only their own Global Address List. That is fine... But two problems exist: 1) If the user from company A opens the address book in Outlook 2003, he/she can list under "All Address Lists" the address list of the company B also. But user from company A cannot access this list. We want that the company users can list only and only their own address list, not the other address lists. I checked all permissions under Security tab of each created company address list. They are ok. Only the company global security group has access to its own company address list. Also there is no Authenticated Users and Everyone group in the security tab. 2) If a company user try to create a new contact in his/her own company Global Address List , he/she cannot create it. I gave the company global security group also Full access right, but that didn't work also. How can a user can create a new contact (or delete) in his/her own company Global Address List? Best Regards Mustafa