The demographic stability of the Swiss Canton of Geneva provided us with the necessary conditions for a follow-up study of the entire childhood population who, having consulted the Child Psychiatry Services between 1963 and 1967, later consulted the adult public psychiatric services (720 cases). We looked for specific clusters of clinical signs which would enable us to differentiate, statistically speaking, the groups of children according to their adult diagnosis. We present here the results for the group of children who were diagnosed at adulthood as drug addicts (DSM III R). We found a specific cluster significantly differentiating these children from the other populations. It includes: a personality disorder (undifferentiated behaviour, and solitary and aggressive behaviour), environmental factors (monoparental, rejecting family) and a lack of mental deficiency.