The effects of a personalized system of instruction (PSI) with and without a same-day retake contingency on the spelling performance of 10 behaviorally disordered students were evaluated. The results indicate more spelling lessons were passed with 100% accuracy when the PSI program was in effect. A further increase in the number of lessons passed occurred when retakes were allowed each day. Individual data for three selected students indicate that their performance increased with PSI and PSI with retakes. From items on a questionnaire administered to students, it was found that the students felt their spelling test performance was higher during the PSI program. The students preferred the PSI spelling program to that of the traditional pre- and posttest spelling procedure (Baseline 1 and 2). The class also preferred the retake component over the non-retake component in the PSI spelling program. Recommendations for classroom use of personalized systems of instruction (PSI) are made.