A Personalized System of Instruction (PSI) program for nontraditional adult learners was developed, implemented, and evaluated. The study objective was to determine if further investigation of use of PSI was worthwhile. From a review of literature and practice of PSI and adult learning, conclusions were drawn regarding major factors to consider when developing and implementing a PSI program for nontraditional adult learners. Suggestions were related to five basic elements of PSI: materials, mastery requirement, self-pacing, peer proctors, and motivational lectures. Two large subpopulations of nontraditonal adult learners were identified as needing the educational assistance PSI offers--persons needing adult basic education and adults in correctional institutions. Three adult basic education classes of a public continuing education institution were selected for implementation of a PSI program; two other classes served as comparison groups. Twenty-five PSI students mastered 48 language and 69 mathematics units. They showed average gains of almost one grade level in reading comprehension and more than one grade level in arithmetic computation and problem solving. No gains were indicated for comparison students. Areas for research were identified for the five elements of PSI. (YLB)