Several studies have been conducted in different countries since policies of deinstitutionalizing the mentally disordered have been implemented. Different explanations of the criminality of individuals with major mental disorders are evaluated that focus on police bias, substance abuse, and the early and late start model. The author proposes two types of offenders with major mental disorders: (1) the early starter displays a stable pattern of antisocial behavior from a young age; and (2) the late starter begins offending only at about the time symptoms of the major mental disorder become apparent. In addition, the author hypothesizes that major mental disorders are not related to the criminality of early starters and that symptoms of major mental disorders may be directly related to the illegal behavior of late starters. Clinical implications for mental health professionals who assess and treat individuals with major mental disorders are discussed. 59 references