This 17-week study will begin with a 2-week methadone stabilization period. Participants will then be randomly assigned to receive a daily dose of either 250 mg of disulfiram or placebo for 12 weeks, while concurrently receiving methadone treatment. All participants will stop receiving study medication at Week 14, at which point they will undergo a 4-week methadone detoxification period. Participants will report cocaine and other drug use, as well as any cocaine cravings that they experience. Cocaine levels will be monitored throughout the study with urine tests. The DBH gene of each participant will be examined to determine its specific make-up and any particular variations.