Scientific research and program evaluation have not played a major role in shaping the development of treatment services and systems in most countries. This has led to disparities in the development, management and monitoring of national treatment systems. In the evaluation of treatment for substance use disorders, the evaluation practitioner will usually be working at one of five levels: single case, treatment activity, treatment service, treatment agency or treatment system. One of the major barriers to undertaking internal program evaluation is the belief that it is a complicated research process best left to those with specific research training. Program managers and staff can plan and initiate an evaluation process for their program if they have access to research expertise when needed for certain parts of the process. There are seven main components of an evaluation process that can be planned and implemented: need assessment; evaluation planning, process evaluation, cost analysis, client satisfaction evaluation, outcome evaluation and economic evaluation. However, evaluation is more than the techniques and technology required to implement these types of activities. It also involves the routine questioning of current practice even if the feedback may be less positive than anticipated. A healthy culture for evaluation is one in which feedback loops are woven into the fabric of the treatment service or system. There are many barriers to evaluation in substance abuse services but these barriers can be overcome with careful planning and commitment to the delivery of evidence-based services.