The more fully one comprehends the nature of the shifts in theoretical and methodological orientation which have been taking place in social psychology during the past two decades, the greater becomes his appreciation of the fundamental contributions made by Harry Stack Sullivan to this highly significant movement in social science. An appraisal of the changes here indicated has been made elsewhere1. Briefly stated the basic trend has been toward what may be called interactional theories of human behavior and personality and away from static atomistic attributive theories, with accompanying efforts to develop methods more appropriate for dealing with dynamic interactional situations. Sullivan's importance in this development is due not only to the fact that he has made the most explicit formulation of interactional theory and practice in psychiatry as such, but that these formulations are highly relevant and significant for the whole field of social psychology. There can be no doubt that he will rank as one of the major contributors to a matured social psychology.