Aim. To assess the prevalence of DSM-III-R axes I and II disorders and the severity of psychiatric symptoms in cannabis users who did not use other illicit drugs . Design. Cross-sectional psychiatric examination of subjects with different patterns of cannabis use: cannabis dependence, abuse and occasional use . Participants. One hundred and thirty-three cannabis users identified through random urine testing of draftees to the Italian army and interviewed after 2-5 days of abstinence from drug use . Measurements. The subjects completed the Beck Depression Inventory, the Spielberger State-Trait Anxiety Index and the 20-item revised Toronto Alexithymia Scale and were then interviewed with the Structured Clinical Interview for DSM-III-R . Findings. The prevalence of co-morbid psychiatric disorders varied with the pattern of cannabis use: 83% of subjects with DSM-III-R cannabis dependence, 46% of those with DSM-III-R cannabis abuse and 29% of occasional users received at least one DSM-III-R psychiatric diagnosis. The severity of depressive, anxious and alexithymic symptoms increased progressively with the degree of involvement with cannabis . Conclusions. In this sample of young men, the risk of associated psychiatric disabilities varied with the pattern of cannabis use. Chronic use of cannabis was associated with a high prevalence of co-morbid psychiatric disorders.