This paper describes a research project sponsored and funded by the State Department's Bureau of International Narcotics and Affairs (INL) on substance abuse and treatment in ten countries. The purpose of the study was to identify promising practices in drug treatment in Europe, Latin America, and Southeast Asia. The steps taken to complete this evaluation are described, including the instruments used and the types of data collected. Also discussed are translation and communication issues as well as examples of other challenges of international evaluation and how these challenges were overcome by the evaluation team.