An interview study was conducted among a group of incoming prisoners in a county jail in Ohio during the summers of 1997 and 1998 to assess their current drug treatment needs. "Incoming prisoners" refers to individuals who were being transferred from this county jail to the state prison system. Marijuana and cocaine were the most commonly tried illegal drugs among the subjects as well as the drugs of choice during the month prior to imprisonment. The Diagnostic Interview Schedule, combined with questions employed in the Drug Use Forecasting (DUF) project, was used to construct the questionnaire for this study. Based on the criteria of DSM-IV diagnoses, 57.5% of those interviewed had exhibited drug dependency at some point in their lives, and 51% were currently dependent on some substance. Thus, more than half of the incoming prisoners were in need of treatment for use of at least one substance. Cocaine dependence was the greatest problem facing this group of inmates, with an especially notable problem among the older females. Younger males were more likely to have current marijuana dependence. The study found that individuals currently dependent on cocaine or opiates perceived that they had a need for drug treatment, while those currently dependent on marijuana did not share this perception.