This study investigated the prevalence of decayed, missing, and filled teeth (DMFT) in a state prison system, using the opening of a new institution as an opportunity to examine a cross-section of the state male inmate population routinely. A representative sample of 178 male inmates was examined by a single dentist, and the results were linked to demographic information. This study found a mean DMFT of 10.5 for inmates aged 18-29, 17.1 for inmates aged 30-44, and 22.4 for inmates over age 44. In the 18-29 age group, white inmates had more filled teeth than blacks (P less than .005) and more missing teeth (P = .06). Missing teeth increased by 0.54 teeth/year of age (P less than .001) and DMFT increased by 0.66 teeth/year of age (P less than .001). The number of decayed teeth was explained using negative reciprocal time incarcerated (-1/T), and declined by 1.30 teeth between the sixth and 12th month of incarceration (P less than .01). This may have been due to a treatment effect, or by selective loss of the population with poorer teeth. Comparison with US employed adults standardized to the study population showed that inmates had more missing teeth at every age, and a greater percent of unmet dental needs.