This study investigates severity of dependence upon heroin, cocaine and amphetamines in a group of 200 heroin users, 75% of whom were not in contact with any treatment agency. For drug takers who were current users of more than one drug, heroin produced more severe dependence than either cocaine or amphetamine and many users of these stimulant drugs reported having experienced no problems of dependence. Severity of dependence was influenced by route of administration as well as type of drug. Heroin taken by injection was associated with more severe dependence than smoked heroin. For cocaine, injection and smoking were associated with equivalent dependence ratings, and both of these routes were associated with more severe dependence than cocaine used intranasally. For amphetamine, there were no differences in severity of dependence ratings for injection, intranasal or oral use. Severity of dependence was correlated with dose and duration of drug use; it was also associated with previous attendance at a drug treatment agency, though dependence problems were also common among heroin users who had never received treatment. Implications of these findings are discussed.