In an attempt to make sense of contradictory findings, meta-analysis was used to review 53 studies that examined counselor self-disclosure (CSD) vs. nondisclosure. CSD, overall, was found to have a favorable impact on clients/participants, with clients/participants having favorable perceptions of disclosing counselors and rating themselves more likely to disclose to counselors who had self-disclosed. Specifically, CSD that (a) revealed similarity between client and counselor; (b) was of negative content valence; or (c) was related to intra- or, especially, extratherapy experiences, had favorable impacts on clients/participants compared with nondisclosure. These types of disclosure resulted in more favorable perceptions of the counselor, especially in the area of professional attractiveness. CSD that revealed similarity between client and counselor also had a favorable impact on clients'/participants' allegiance-specifically, on their willingness to return-to disclosing counselors. Significant moderators of the impact of CSD on clients included researcher bias for or against CSD, type of "session" (e.g., written transcript, interview, real session), timing of CSD (whether before or after client self-disclosure), verb tense of extratherapy CSD, experimental setting, type of control group, and the number of CSDs in the experiment. Clinical implications include that CSD may be beneficial for building rapport, strengthening alliance, and eliciting client disclosure, with similar CSD being especially beneficial.