The offenders participated voluntarily in a treatment outcome study and underwent a psychological and psychiatric assessment after admission. The study excluded those who were psychotic, severely confused, or unable to concentrate. The interviews used the Composite International Disorder Interview to identify Axis I disorders and the International personality Disorder Examination to identify Axis II disorders. Results revealed that the most prevalent Axis I disorders were substance abuse (75.7 percent), mood disorders (51.3 percent), and anxiety disorders (40.3 percent). In addition, 86.8 percent of the participants had a personality disorder, most often from the B cluster of Axis II. A total of 42.1 percent of the participants received the diagnosis of personality disorder not otherwise specified. Results also revealed comorbidity of mood and anxiety disorders with personality disorders in 61 percent of the participants and with drug abuse in 47 percent of the participants. Results indicated that the prevalence rates of the separate disorders were much higher in the forensic participants than in the general population. Findings emphasized the importance of the use of standardized diagnostic instruments and the assessment of a broad range of disorders. Tables and 38 references (Author abstract modified)