For approximately 14 consecutive evenings each quarter, trained local staff obtain voluntary and anonymous urine specimens and interviews from a new sample of arrestees. In each site, approximately 225 males are sampled. In some sites, approximately 100 female arrestees are also interviewed. Third quarter results from July to September 1989 were the following: (1) the percentage of males testing positive ranged from 53 percent in San Antonio to 84 percent in New York; (2) more than 60 percent of the tested female arrestees were positive in 10 of the 16 cities; and (3) cocaine was the most frequently detected drug for most male and female arrestees. This information can be used to plan the allocation of law enforcement, treatment, and prevention resources, as well as to gain an indication of the impact of local drug use reduction efforts. 2 tables.