Data concerning the epidemiology of drug abuse in the United States are presented in this paper. The paper includes an integrating approach from various data sources: national, state, and local level; surveillance systems; and outbreak investigations. An analysis of trends and patterns of drug abuse are discussed, both from the perspective of historical development and the current situation. Analyses focus on changes in levels of use for different drugs as well as changes in user characteristics and consequences of use. Current studies concerning the epidemiology of drug abuse in special populations and findings from recent field investigations are presented. Future research directions in the field of epidemiology from a national perspective are outlined.