The authors determined suicide attempt characteristics in 160 opioid-dependent subjects. 3 aspects of suicide vulnerability were also examined: familial aggregation of suicidal behaviours, degree of aggression/impulsivity, & smoking. 48% of subjects had a personal history of suicide attempt. A personal history of suicide attempts was associated with an early onset of heroin use but not with gender differences. A family history of suicide was a progressive risk factor for suicide attempt. Subjects with a personal history of suicide attempt had a higher degree of aggression/impulsivity, & smoked more cigarettes. (44 refs.)