Research documents that since the 1940's, most inner-city areas have maintained large populations of drug users that are heavily involved in crime. Although the sizes of these populations tend to fluctuate and the nature of their drug use may vary, their numbers have remained significant, and current trends suggest this pattern will continue. In recent decades, a number of "epidemic" periods have been documented, during which large numbers of new recruits to the heroin world have emerged. The 1967-69 and 1973-75 periods have been charted as the more current epidemic periods, and analyses of current populations of heroin users show that most were initiated during these times. The majority of new users come from the younger age groups. Most of the youthful heroin users studied were recruited during the 1973-75 epidemic period. Although crime and drug use, notably heroin use, may not be causally linked, their rates tend to parallel one another in communities marked by high unemployment rates, financial assistance, and poverty. Nonheroin drug-using juveniles begin criminal activity at a young age, maintain levels of offense behavior almost as high as that of their heroin-using counterparts, and do so for purposes other than drug-use support. The history of drug use during the last 20 years has suggested that "fad" drugs come and go and that each new "fad" brings new users to the drug street scene. 5 notes, 3 tables, and 66 references