Two studies employed a known-groups validation strategy to evaluate a Thematic Apperception Test (TAT) scoring system purported to measure personal problem-solving skills, the Personal Problem-Solving System (PPSS). In Study 1 clinicians rated the records of 46 mental health outpatients for the presence of personal problem-solving skills deficits. Verbatim TAT transcripts from these patients were blindly scored using the PPSS. Participants predicted to demonstrate problem-solving deficits obtained lower PPSS scores. In Study 2 a psychiatric sample (n = 47) and a community-based comparison group (n = 47) completed a life history questionnaire, a checklist of problems currently experienced, a measure of psychiatric symptoms, and responded to 3 TAT cards. TAT responses were again blindly scored using the PPSS. In contrast to the comparison group, psychiatric patients checked a greater number of current problems, endorsed more psychiatric symptoms, and obtained lower scores on the PPSS. A discriminant function analysis using PPSS scores correctly classified 72% of these participants. PPSS scores predicted group membership even after controlling for differences in age, education, the number of problems experienced, and psychiatric symptoms. This combination of variables correctly classified 92% of the participants. Results of both studies are interpreted as supporting the discriminant validity of the PPSS.