Is therapist self-disclosure a therapeutic technique or a therapeutic mistake? Is it useful? Is it ethical? This study attempts to address this controversy among therapeutic modalities by asking clients about their perceptions of self-disclosure and nondisclosure. Eighteen people (16 women, two men), currently in therapy in two Canadian cities, generated 157 incidents of both disclosure and non-disclosure. The incidents were first coded as helpful or unhelpful. Cross-tabulation of the results showed that disclosures were more than twice as likely to be experienced as helpful; non-disclosures were twice as likely to be unhelpful (chi(2) (3, N = 157) = 14.439, p <= 0.002). One-quarter of these incidents was coded by two independent raters; inter-rater reliability was high (Pearson corr. ranged from 0.755 to 1.0, p <= 0.01). The data was then sorted, using the Constant Comparison method, into themes, starting with, but not limited to, the themes suggested by the literature. The greatest single effect was on the therapeutic alliance, both positive and negative. Clients' perceptions of helpful disclosures and non-disclosures generally supported therapists' rationales. There was also some evidence that when clients found disclosures unhelpful, the reasons also supported theoretical rationales against disclosing. Rather than simply supporting either position in the controversy, this study suggests that skill, or lack of it, was the intervening variable that affected the perceptions of both techniques. Further research on the effects of skill on both disclosure and non-disclosure are warranted. This study has implications for both researchers and practitioners.