The main aim of this study was to examine the role of illicit drug use before the age of 18 years in developing a criminal career. The study included 7577 18-year-old men conscripted for military service in Stockholm County in 1969/1970. At enrolment they answered questions regarding alcohol and illicit drug use, social background, behavioural factors and health. Data on adult and adolescent criminality were obtained from official registers from the age of 15 to the age of 43. Subjects with self-reported drug use were registered significantly more often (p