Research has shown that drug abuse treatment can help many individuals. Yet funding is often lacking for treatment because these programs compete for scarce resources with other important and effective social programs. This study shows how drug abuse treatment programs can be made more attractive to decision makers and funding agencies by first highlighting why economic evaluation is a critical component of drug abuse treatment research. Next, an evaluation methodology is presented that can be followed by program staff and researchers. The evaluation methodology includes aspects of cost-and-outcome analysis, cost-effectiveness analysis, and benefit-cost analysis. Methods and findings are then discussed from most of the major economic evaluation studies of drug and alcoholism treatment. Lastly, guidelines for conducting future economic evaluations are presented along with suggestions for how the results can be used for policy purposes and program planning.