The author's model for structural analysis of social behavior (SASB) is combined with Markov analysis to describe a critical incident in psychotherapy. The incident involved the acting out of pathological process, followed by the development of healthier alternatives in the context of Gestalt therapy. The SASB model classifies interpersonal transactions in terms of focus (i.e., other, self, or introjection), affiliation, interdependence (i.e., dominate-submit to, give autonomy-take autonomy) and topic (i.e., primitive basics; approach-avoidance; need fulfillment, contact, nurturance; attachment; logic and communication; attention to self-development; balance in relationship; intimacy-distance; and identity). Results suggest that the model is effective at describing dyadic interaction; addition of Markov chain procedures offers a promising methodology for defining pathological and constructive social process and the relation between the two. (28 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.