Because we do not fully understand the cause of drug abuse, we do not currently have specific therapy for the abuse phenomenon. It is likely that those patients who abuse drugs are not a homogeneous treatment group. The patients seen most frequently because of medical complications probably represent only a small percentage of the total number of drug abusers. The medical complications of drug abuse affect almost all organ systems, and may result acutely from overdose or may not become apparent until after prolonged or recurrent use. Special emphasis has been placed on recognizing the key points of the physical examination in the overdose setting and in the drug-abusing patient that will give clues as to the nature and degree of the drug abuse. It is not clear whether drug abuse causes behavioral problems or vice versa. Physicians need to develop the medical expertise necessary to care for patients with drug abuse problems. Special attention is called to new drug abuse problems: complications associated with phencyclidine, amyl nitrate, and layman's remedies; acute and pulmonary complications; rhabdomyolysis; the brown heroin syndrome; and methylphenidate abuse. Although each of these complications has individual importance, a high incidence of alcohol use and smoking further compromises the general health of drug-abusing patients. Treating all of the medical complications of drugs must be viewed as only the beginning of a therapeutic attempt to restore these patients to a more physically and emotionally healthy life.