Depot Naltrexone Treatment of Opioid Dependent Parolees

Inclusion/Exclusion Criteria. To be eligible to participate, participants must: * sign an informed consent form; * be between the ages of 18 and 55; * have a diagnosis of opioid dependence according to DSM IVTR criteria; and * be in good general health as determined by complete physical examination and laboratory tests; * have been assigned to a probation/parole period of at least six months; (except those participants not on parole/probation, see note below); and * have a negative result for urinary opioids and must self report being at least 3 days opioid free. Participants may have a diagnosis of alcohol dependence so long as they do not have severe alcohol dependence that requires medical supervision for alcohol withdrawal. Participants with the following characteristics will be excluded from study participation: * current severe alcohol dependence that requires medical supervision for alcohol withdrawal; * current psychosis, dementia, mental retardation, or history of schizophrenia; * significant clinical abnormalities in hematology, chemistry, or urinalysis; * significant clinical cardiovascular, neurological, hepatic, renal, pulmonary, metabolic, endocrine, or gastrointestinal disorders; * female subjects who are pregnant or lactating, or female subjects of childbearing potential who are not using birth control (oral contraceptives, barrier (diaphragm or condom) plus spermicide, or levonorgestriel implant); * subjects who have taken an opioid antagonist within the prior 6 months; and * current diagnosis of chronic pain disorder.