This paper describes the personalized system of instruction (PSI), a teaching method based on a high student involvement in the learning process, immediate feedback, mastery learning, and careful planning and instructional design of the course content. With PSI, students proceed through the course at their own pace and are required to demonstrate mastery of each component before proceeding to the next; teaching materials are largely text-based; proctors provide tutorial support; and lectures and demonstrations are intended to motivate students rather than deliver course content. PSI is deemed especially useful in courses where content is primarily skill development or cognitive information and for courses with large enrollments and limited resources. This paper describes use of the PSI method in a computing course at Texas Tech University. Reported difficulties include: procrastination; difficulty in recruiting proctors; cheating on tests; organizing the course so that the modules are well-articulated and based on a logical hierarchy; complaints that learning small isolated bits of information inhibited synthesis of information; appropriateness of the PSI model for the course; a greater-than-normal instructor time commitment; changed teaching role; keeping module materials current; and varied student learning styles. (Contains 11 references.) (CH)