This background paper examines evidence for the effectiveness of treatment for drug abuse and evaluates the role of drug abuse treatment as a strategy to prevent Human Immunodeficiency Virus (HIV) spread. Because most intravenous (IV) drug users are not in treatment, the study also examines other approaches to HIV prevention. The remainder of the first chapter summarizes the main findings. Chapter 2 reviews the current situation regarding drug use and HIV infection in the United States. Chapter 3 provides background information about the drugs of abuse and various treatment modalities. Chapters 4 and 5, respectively, review the existing literature on the effectiveness of drug abuse treatment and examine the role of drug abuse treatment in preventing HIV infection. The appendices describe the method of study and the drugs of abuse other than narcotics and stimulants; summarize a cost-benefit analysis of drug abuse treatment; and review highlights from the most recent National Drug and Alcoholism Treatment Unit Survey. (LLL)