The review describes overall current patterns of the use of psychoactive legal and illegal drugs, the epidemiology of substance use disorders, trends over time in patterns of use, and difference in drug use based on gender, age, geographic location, socioeconomic status, and ethnic group. The prevalence, patterns, and trends in drug use and abuse can be tracked using data systems that compile statistics based on individuals who are involved with medical, treatment or criminal justice agencies, and using surveys designed to determine the extent of drug use among the noninstitutionalized population. 15 tables, 1 figure, and 90 references