Mental disorder diagnoses among 51 patients, made by a group of 20 family physicians, were compared with diagnoses generated by the Diagnostic Interview Schedule (DIS). Processes of diagnosis, decision making, and treatment planning were then examined through structured physician interviews and chart audits. In this study, 75 of 94 DIS diagnoses (79%) were undetected. During interview and chart audit, the physicians were found to have consistently under-estimated, misinterpreted, or neglected psychiatric aspects of care among a majority of patients in the study. These physicians had all satisfactorily completed a psychiatry curriculum designed for family physicians. Analysis of these results suggests that a mental health role is often not integrated into primary care practice, regardless of physician performance during psychiatric training experiences. Assumption of this role appears to be state dependent on involvement with a psychiatric treatment setting. Primary care practice patterns do not seem to result in application of appropriate skills and therapeutic attitudes to detect, diagnose, and correctly manage the majority of mental disorders that occur. The need is reaffirmed for active collaboration between mental health professional and primary care providers in training and in incorporation of psychiatric skills into primary care practice.