This article introduces Self-System Therapy (SST), a brief, structured psychotherapy for the treatment of depression. SST conceptualizes depression as a failure of self-regulation and is intended for individuals whose depression and/or premorbid functioning are characterized by particular problems in self-regulation. This article provides an overview of SST, including its origins in basic and clinical research on self-discrepancy theory and self-regulation, the hypothesized etiological role of self-regulation in depression, the primary components of the treatment, and comparisons of SST with other psychotherapies for depression. The general structure of a course of treatment with SST is outlined, and a case example is presented to illustrate the goals and strategies of each phase. © 2003 American Psychological Association D12.