Ninety-six confirmed heroin addicts requesting a heroin maintenance prescription were randomly allocated to treatment with injectable heroin or oral methadone. Progress was monitored throughout the next 12 months by research workers operating independently of the clinic. Heroin can be seen as maintaining the status quo, with the majority continuing to inject heroin regularly and to supplement their maintenance prescription from other sources; it was associated with a continuing intermediate level of involvement with the drug subculture and criminal activity. Refusal to prescribe heroin while offering oral methadone constituted a more confrontational response and resulted in a higher abstinence rate, but also a greater dependence on illegal sources of drugs for these who continued to inject. Those offered oral methadone tended to polarize toward high or low categories of illegal drug use and involvement with the drug subculture, and were more likely to be arrested during the 12-month follow-up. There was no difference between the two groups in terms of employment, health, or consumption of nonopiate drugs. Refusal to prescribe heroin resulted in a significantly greater drop out from regular treatment.