The purpose of the present study was to enlighten the prognosis for young delinquents, who had been subject to a mental report for the court, regarding later psychiatric illness, mortality and criminal relapse. The study was retrospective based on register information about psychiatric admissions, death courses and later criminal commitments. After less than 20 years, 11% were found psychotic, 22% had died and 90% of the survivors had committed a total of 831 criminal offences from drunk driving to homicide. We conclude, that at present no institutions in Denmark are suitable for the treatment of young delinquents with severe criminal records. Most of the young delinquents have psychological and behavioural disturbances from childhood, and early intervention is needed followed by careful documentation and follow-up studies in order to improve the prognosis for these young people.