Substance abuse is a major public health problem in the United States today. Studies are showing increasing evidence of the serious medical and psychosocial consequences of drug use across all age groups. Of great concern are the problems of infants born to addicted mothers, the increased incidence of cardiovascular complications in young people due to cocaine use, and the extremely high risk of exposure to human immunodeficiency virus. There is no socioeconomic group that is left untouched by substance abuse. Yet, for various reasons this disease is probably the most ignored or underdiagnosed disease in the primary care setting. This article provides information about addiction and suggests key areas for history taking, physical exams, and collection of laboratory data that may help in primary care screening. When concrete information about the consequences of drug use is provided to addicts they may be motivated to seek treatment without feeling threatened.