Economic considerations influence the substance user treatment system. These considerations influence who gets treatment and for how long, as well as determining what services they receive and in what setting. Current medical literature argues that maintenance treatment reduces risk-taking behavior, such as injection drug use and needle sharing. Treatment also reduces the mortality associated with abuse of opiates by injection and can cause decreases in costs incurred by the criminal justice system and social services agencies. This suggests the need for complex economic evaluations of a maintenance treatment to find out the optimum treatment program. This paper describes methods of economic evaluation in health care and reviews the methodology of cost-utility analysis in economic evaluations of methadone maintenance treatment.