A total of 932 adolescent psychiatric in-patients were followed up 15-33 years after hospitalization by record linkage to the National Register of Criminality. On the basis of the hospital records the patients were rediagnosed according to DSM-IV and scored on data postulated to be predictors of later delinquency. The factors were investigated by Kaplan-Meyer survival analysis and Cox regression. Cox analysis showed that, in males, main diagnosis (relative risk (RR)=2.9, 95% confidence interval (CI)=2.0-4.2), verbal abuse at home (RR=1.5, CI=1.1-2.0), disciplinary problems at school (RR=1.7, CI=1.2-2.5), and violating ward rules during hospitalization (RR=1.6, CI=1.2-2.2) were strong and independent predictors of delinquency. In females, main diagnosis (RR=2.6, CI=1.6-4.2), concurrent psychoactive substance use disorder (RR=2.9, CI=1.9-4.2), verbal abuse at home (RR=1.5, CI=1.0-2.1), and disciplinary problems at school (RR=1.6, CI=1.1-2.5) were strong and independent predictors of delinquency. Among males who violated ward rules and received a diagnosis of disruptive behaviour disorder, psychoactive substance use disorder or personality disorder at index hospitalization, as many as 77.6% had a criminal record at follow-up.