Inclusion Criteria:

• Male or female individuals, ages 18 and above, meeting current DSM-IV criteria for opioid dependence.
• Subject has voluntarily given informed consent and signed the informed consent document.
• Able to read English and complete study evaluations.

Exclusion Criteria:

• Regular use of benzodiazepines.
• Psychotic or otherwise severely psychiatrically disabled (i.e., suicidal, homicidal, current mania);
• Significant underlying medical conditions such as cerebral, renal, thyroid or cardiac pathology which in the opinion of study physician would preclude patient from fully cooperating or be of potential harm during the course of the study;
• Abstinent from opiates for more than four weeks prior to naltrexone initiation.
• Medical problems that would preclude naltrexone treatment, such as laboratory evidence of significant hepato-cellular injury as evidenced by abnormal liver enzyme tests including SGOT and SGPT (> three times normal) or elevated bilirubin levels), and a history of cirrhosis.
• Women who are pregnant, nursing or refuse to use a reliable form of birth control (as assessed by pregnancy tests during initial evaluation for naltrexone, and every two weeks during the course of the study).