This article presents an integrated conception of the self based on cognitive and interpersonal theories. Implications for clinical practice are outlined, which include understanding the therapeutic relationship as a laboratory and change as involving self-expansion. Implications for clinical research are also presented and exemplified by two strategies, which are demonstrated in a single case study of a patient who successfully underwent a brief-term treatment. The first involves the use of Interpersonal Scenarios, which are structured idiographic vignettes scaled on several parameters, to measure change between psychotherapy sessions. The second involves the use of the Structural Analysis of Social Behavior, a measure of interpersonal process, and the Experiencing Scale, a measure of emotional involvement, to measure change within a session. © 2001 John Wiley & Sons, Inc. J Clin Psychol 57: 307–330, 2001.