Using a two-stage case identification method, the Japanese version of the General Health Questionnaire (GHQ) and the Japanese modified Diagnostic Interview Schedule (DIS-JM), patients in a general medicine clinic in Japan were assessed for psychiatric disorders (DSM-III categories) during a 12-month period. The lifetime prevalence of all psychiatric disorders was 30.6%, excluding tobacco dependence. The most prevalent diagnoses were alcohol abuse and dependence 9.4%, psychosexual dysfunction 5.9%, and major depressive episode 4.7%. The predominant disorders in males were alcohol abuse and dependence and tobacco dependence, and in females (aged 55-80 years), the most striking disorder was organic brain syndrome. The validity of the GHQ was examined against the DIS-JM based on DSM-III as external criteria. A cutoff point between 7 and 8 is suggested.