Changes and adaptations are always necessary after the deployment of a multi-agent system (MAS), as well as of any other type of software systems. Some of these changes may be simply perfective and have local impact only. However, adaptive changes to meet new situations in the operational environment of the MAS may impact globally on the overall design. More specifically, those changes usually affect the organizational structure of the MAS. In this paper we analyze the issue of design change/adaptation in a MAS organization, and the specific problem of how to properly model/design a MAS so as to make it ready for adaptation. Special attention is paid to the Gaia methodology, whose suitability in dealing with adaptable MAS organizations is also discussed with the help of an illustrative application example.