To demonstrate how a novel computer joystick coding method can illuminate the study of interpersonal processes in psychotherapy sessions, we applied it to Shostrom's (1966) well-known films in which a client, Gloria, had sessions with 3 prominent psychotherapists. The joystick method, which records interpersonal behavior as nearly continuous flows on the plane defined by the interpersonal dimensions of control and affiliation, provides an excellent sampling of variability in each person's interpersonal behavior across the session. More important, it yields extensive information about the temporal dynamics that interrelate clients' and therapists' behaviors. Gloria's 3 psychotherapy sessions were characterized using time-series statistical indices and graphical representations. Results demonstrated that patterns of within-person variability tended to be markedly asymmetric, with a predominant, set-point-like interpersonal style from which deviations mostly occurred in just 1 direction (e.g., occasional submissive departures from a modal dominant style). In addition, across each session, the therapist and client showed strongly cyclical variations in both control and affiliation, and these oscillations were entrained to different extents depending on the therapist. We interpreted different patterns of moment-to-moment complementarity of interpersonal behavior in terms of different therapeutic goals, such as fostering a positive alliance versus disconfirming the client's interpersonal expectations. We also showed how this method can be used to provide a more detailed analysis of specific shorter segments from each of the sessions. Finally, we compared our approach to alternative techniques, such as act-to-act lagged relations and dynamic systems and pointed to a variety of possible research and training applications. (PsycINFO Database Record (c) 2014 APA, all rights reserved).