In a prospective longitudinal epidemiological study with assessments at age 8, 13 and 18 the prevalence rate for psychiatric disorders remained constant at about 16%. The sex ratio for severe disorders was male dominated even in adolescence, which was a consequence of the high rate of unsocialized disturbances of conduct in boys. Persistence of psychiatric disorders between age 13 and 18 was about 50%, as had previously been the case between age 8 and 13. One child in four suffered from a psychiatric disorder for at least 10 years. In childhood, conduct disorders had a very poor prognosis and emotional disorders a very good one. In adolescence, the course of disorders depended on an interaction between diagnosis and gender. Boys with unsocialized disturbances and girls with emotional problems had a poor prognosis.