The final sample consisted of 2,660 inmates, of whom 1,967 were released and 639 were still actively being held in jail. The results showed that the rate of intravenous drug use was highest (43 percent) in male inmates between the ages of 36 and 40. Younger inmates had progressively lower rates of intravenous drug use, while those incarcerated for longer periods of time and women had high rates of intravenous drug use. Although the overall rates of drug use did not change significantly over the 11-year study period, patterns of drug use did change in that rates of heroin use decreased, the highest prevalence of intravenous drug use toward older age groups, and there was an increased rate of cocaine use among male inmates. 8 tables, 4 figures, and 12 references