During the last few centuries, and particularly in recent decades, problems result­ ing from the excessive use of drugs and alcohol have spread virtually as an epidemic to every country in the world and to almost every community. Abuse of alcohol and drugs is related to numerous other health problems, such as the spread of acquired immune deficiency syndrome (AIDS) on all continents. Health and social services today cannot afford to ignore this crisis since it affects all levels of society and manifests itself in diverse health and social problems. In recent years, the World Health Organization has received numerous requests for training material for physicians in this field. This manual therefore meets an urgent need. The availability of new data and the dearth of suitable textbooks have made its preparation mandatory. The influence of sociocultural factors on drug dependence and alcohol­ related problems-on their cause, development, and consequences as well as on their treatment and prevention-has been taken into account in the preparation of this manual in order to ensure that its usefulness is not limited to one country or region. It has been prepared primarily for the teaching of physicians and medical students, although much of it is relevant to the training of nurses, midwives, health educators, primary-care workers, medical social workers, counselors, and psychologists. In fact, suggestions have been included for adapting the manual for use in the training of such varied groups of students.