"Environmental Psychology and Policy Research Unit University of St Andrew, UK Starting from the famous Lewinian assumption that "there is nothing so practical as a good theory" (Lewin, 1951) the importance of paying more specific attention to various theories of the psychological tradition , for the present and future development of people-environment studies, is discussed. First the possibility of considering environmental psychology only as a specific domain of applied psychology is considered.Then the tendency to oppose 'basic' and 'applied' psychology is contrasted . We outline the importance of developing environmental psychology not as a simple further domain of applied psychology, but as a "psychology of interface" between on one hand the interdisciplinary domain of the people-environment studies and on the other hand the more specific theoretical interests of various areas of psychological research, traditionally focused on specific psychological processes."