The data used in this study were from the large-scale longitudinal survey, "Young in Norway." Lifetime rates and frequency of cannabis use during the past year were assessed at all three waves of data collection. In addition to measuring the personal substance use, antisocial behavior, and criminal behavior of the sample at various times, the study also obtained data on peers' substance use and criminal activities, parental social class, and symptoms of anxiety. The study found an excess of psychosocial problems among drug users in the general population of young adults in Norway, notably among users of ecstasy and other Class A drugs. Compared to nonusers of drugs, "pure" cannabis users also tended to have a deviant profile, despite the fact that the majority had taken the drug only a few times during the past year. The hypothesis that ecstasy users in their early 20's are more likely than their teenage counterparts to be well adjusted was not supported. They were characterized by excessive use of other substances, a less favorable psychosocial family background, a preponderance of mental health problems, and elevated rates of criminal offending as well as frequent involvement in other antisocial behaviors. 4 tables and 83 references