In this paper co-authored with Barbara Maynes,we outline a developmental view of OD. We show that Argyris “theory in use” points to different levels of mental growth, both social-emotional and cognitive. These levels are seen as the program from which theories of action arise in contributors to an organization. An early version of CDF called DSPT (developmental structure/process tool) is used to substantiate this claim. In the article, we explain the differences between two executives’ theory of action and analyze the dynamic of a six-member team on developmental grounds. By way of close analysis, we show that theories of action are developmentally grounded, and are thus open both to maturation over the life span and to interventions like developmental coaching. We come to the conclusion that developmental assessment of executives and teams should become a vital part of in-house development and of OD intervention. Source: Journal of Management Development, vol. 21.9, 702-729, 2002.