Over 90% of therapists self-disclose to clients (Mathews, 1989; Pope, Tabachnick, & Keith-Spiegel, 1987; Edwards & Murdock, 1994), however, the implications of therapist self-disclosure are unclear, with highly divergent results from one study to the next. The goal of this paper was to review the empirical literature relevant to therapist self-disclosure, and provide the reader with a comprehensive understanding of the factors that affect, and are affected by, therapist self-disclosure. Findings are organized into an integrated model examining the who, what, when, why, and how of therapist self-disclosure. In addition, training implications and suggestions for future research are provided.