This evaluation of the effectiveness of a computer assisted instructional program in basic literacy skills for inmates in a county jail covers the first year of the program. Instructional materials used were developed by Control Data Corporation for use on the PLATO system, and consisted of lessons in vocabulary, reading, spelling, arithmetic computation, and arithmetic problem solving. The reactions of both the prison population and the administrative staff of the Bexar County Detention Center (San Antonio) and their involvement in the program are discussed. Achievement gains of prisoners participating in CAI are compared with those of prisoners in a traditional instruction group, and some suggestions are offered for more effective use of CAI both for inmates and staff development courses. (RAO)