Designed to provide each city with information for detecting changes in drug use trends in arrestees, Drug Use Forecasting information can be used to plan the allocation of law enforcement treatment and prevention resources and to gain some indication of the impact of local drug use reduction efforts. Drug use often is higher in female than male arrestees. During the second quarter of 1989, more than 50 percent of female arrestees in each city tested positive for a drug at time of arrest. DUF data consistently have shown amphetamine use to be limited to arrestees on the West Coast. For most cities, the need for heroin treatment is second to cocaine treatment. An analysis of DUF collected information from arrestees in 20 cities in 1988 revealed that the majority had failed to finish the 12th grade. The dropout rates among arrestees emphasized the limitations of surveys of drug use in senior high school students. 6 figures and 5 tables