A randomized study is planned over 5 years to evaluate the effectiveness of the Therapeutic Workplace in promoting naltrexone ingestion and abstinence in unemployed opiate-dependent injection drug users. Participants will be offered an opioid detoxification and naltrexone induction. Participants who complete the naltrexone induction will be randomly assigned to one of two groups. Both groups will be invited to work in the Therapeutic Workplace and prescribed naltrexone for 26 weeks. The groups will differ in the contingencies imposed to work and earn salary. Work Plus Naltrexone Contingency participants will be required to ingest naltrexone to work, and will receive a brief pay decrease for missing a dose. Work Plus Naltrexone Prescription participants will be prescribed naltrexone, but will not be required to ingest it to work. This study will provide a rigorous evaluation of a novel employment-based intervention, the Therapeutic Workplace, to promote naltrexone ingestion and drug abstinence in a population of injection drug users who are at considerable risk of spreading or contracting HIV infection. Hypotheses being tested in this study are: Naltrexone ingestion will be maintained in the group exposed to the employment-based naltrexone treatment significantly more than the group exposed to usual-care treatment package. Opiate abstinence will be maintained in the group exposed to the employment-based naltrexone treatment significantly more than the group exposed to usual-care treatment package.