A comprehensive computerized system for classifying prison inmates into 1 of 10 groups according to differences in their scores on sections of the MMPI was applied to the MMPI scores of 641 male prisoners at the Utah State Prison. Results were compared with their scores on intelligence and aptitude tests, with results of the Bipolar Psychological Inventory (BPI); and with demographic data, criminal background information, and current offense information. Of the MMPI samples analyzed, 66 percent were classifiable using the computerized system. An additional 22 percent were manually classified. A total of 5 percent were invalid and 7 percent were unclassifiable. Previous psychiatric hospitalization was the only demographic variable to differ significantly across the 10 groups. Educational achievement and intellectual ability differed significantly across the groups. BPI scores were significantly different on 8 of the 10 scales. Significant differences were found among the groups for age at first arrest and number of times in prison. Burglary and second degree murder represented significant differences across groups; however, the number of inmates whose current offense was second degree murder was small. Three factors of prison adjustment (number of major write ups per year, number of minor write ups per year, and likelihood of placement in the protection unit) differed significantly among the groups. This system represents a dynamic, empirical method for classifying prison inmates, and can be generalized to a State prison population. As additional data are collected using the system, automated interpretation systems might be developed. Tables and a list of 30 references are included.