The sample design was a stratified two-stage selection with the probabilities proportional to the size of the correctional facility. The sample was selected independently from two frames, one for males only and a second that allowed an oversample of females. Interviewers visited each selected facility and selected a sample of inmates using predetermined sampling procedures. In 1986, 13,711 interviews were conducted at 275 facilities from a sample of about 15,000. Drug use history was determined directly from inmate responses. Inmates reported high levels of drug use prior to the commission of the crime for which they were incarcerated. Nineteen percent were using a major drug on a daily or near daily basis. Such drug users were the least likely of the inmates to have been employed and the most likely to have been both unemployed and not seeking work. Major drug users were more likely than nonusers to report that they received income from illegal activities during the time they were last free. 17 tables.