The author reviews general principles for assessing, intervening in, and treating adolescent drug abuse. Assessment involves uncovering the extent of the drug problem and the reasons behind it, including the role of family psychodynamics. In the intervention phase, the clinician should clearly explain the diagnosis to the family and firmly recommend further actions, being prepared to encounter resistance. Treatment should enable the adolescent to become free of acute drug effects, understand the disorder, and become physically and emotionally capable of abstinence. Involvement in mutual self-help groups modeled after Alcoholics Anonymous is helpful in achieving long-term abstinence. The author also discusses trends in adolescent drug abuse, treatment of medical and psychiatric complications of drug use, and strategies for handling violent drug abusers.