Converging evidence suggests that disulfiram is a promising treatment for cocaine dependence. We study the cost-effectiveness of providing disulfiram to methadone-maintained opioid addicts in a randomized clinical trial setting. Our economic evaluation is based on a double blind clinical trial in which 67 cocaine-dependent methadone-maintained opioid-dependent subjects were randomized to get the additional treatment of disulfiram or placebo in a 12-week trial. Outcome measures used are the number of days of cocaine use and grams of cocaine per week. Cost measures used are the cost of providing standard methadone treatment and the incremental cost of adding disulfiram to the standard treatment. Cost measures of standard and disulfiram-enhanced treatment were collected retrospectively from the provider. Results from this cost-effectiveness analysis imply that, even though disulfiram increases slightly the cost of methadone treatment, its increase in effectiveness may be important enough to warrant its addition for treating cocaine dependence in methadone-maintained opiate addicts.