This session begins with a presentation of a ''person-environment'' conceptual model that was designed to explore the development processes underway in informal hillside communities in Trinidad. The conceptual model is then applied to ongoing regional planning projects in southern Trinidad, and ‘sustainable neighbourhood' planning initiatives in Montreal. The importance of coming to understand the development processes that are presently underway in residential environments and the roles of individuals, community groups, and government institutions in promoting collaborative environmental change are highlighted.