The authors emphasize a number of significant issues in substance abuse among children and adolescents. First, the prevalence of drug use has increased over the past 5 years, and the age at first use has decreased. Second, substance abuse in the family is a major risk factor for adolescent substance abuse. Third, pediatricians are ideally situated to screen for substance abuse; they can perform the initial assessment and provide support, counseling, referral, and substance abuse education/prevention for adolescents and their families. Fourth, substance abuse should be included in the differential diagnosis for any child or adolescent who exhibits a change in behavior (school performance/attendance and family relationships). Fifth, substance abuse and dependence are multifactorial and multidimensional disorders that have no single etiology. Among the factors discussed as influences in substance abuse disorders are neurobiological factors, genetic factors, family and environmental factors, personality factors, and psychological factors. Descriptions of the characteristics and effects of individual drugs cover cocaine, heroin, marijuana, hallucinogens, alcohol, inhalants, sedatives/hypnotics, and amphetamines. Routes of delivery and comorbid psychiatric disorders associated with substance abuse are also discussed. A discussion of treatment encompasses 12-step groups and inpatient treatment. 5 tables and 13 suggested readings