This is the first volume of the long-awaited research report on a much discussed study on the prescription of heroin and other narcotics to chronic heroin addicts in Switzerland. Data were collected over a period of 3 years on a cohort of 1,035 chronic heroin addicts who had failed in drug-free or methadone substitution treatments and who were prescribed heroin, morphine or methadone within the framework of a comprehensive care program. According to the findings of the study, heroin maintenance is considered to have a positive effect on both patients and their social environment due to an improvement in health and social status of the patients as well as a significant decrease in drug-related delinquency. This report provides a unique source of information on pharmacological, medical and psychosocial aspects of heroin maintenance. It is indispensable reading for psychiatrists, doctors, and social workers working with drug addicts as well as for pharmacologists, social scientists, criminologists and public health officials concerned with the treatment and management of drug addiction.