The data came from the following Drug Use Forecasting (DUF) System sites of NIJ: Los Angeles, San Diego, Phoenix, New Orleans, and New York City. Between September and December 1987 a total of 516 females and 991 males were interviewed and had their urine tested. More than half tested positive for illicit drugs. Females, predominantly white females, were more likely than males to report having injected drugs. From one-fourth to one-half of the subjects reported needle sharing. By failing to focus enough resources on addressing the drug abuse and AIDS problem in arrestees and probationers, the nation is losing an important opportunity to reach the largest pool of serious drug abusers entering the criminal justice system. Additional recommendations, tables, figures, and 20 references.