We describe the epidemiology of crime between ages 15 and 30 in a population-based sample. We received police register data for 5405 males and females, representing the children born in Finland in 1981. We classified crimes into drug, violent, property, traffic, drunk driving, and sexual crimes, excluding minor traffic offenses. Of males, 60% and of females, 25% were registered for offending. For males, prevalence peaked in late adolescence, while for females, there was no peak age. Offending frequency remained stable for male offenders but was lower among adolescent female offenders. All crime types overlapped each other. Crime accumulated: 1% committed 34% of male and 56% of female offenses. In conclusion, the adolescent peak in offending reflects peaking prevalence among males, not females, nor frequency of offending among offenders. The crime problem is focused on two key groups: late adolescent males and the few males and females in whom crime concentrates.