A study investigated the effects of using the Personalized System of Instruction (PSI) model in distance education. The PSI version of the course (PSI-P) was compared to a version of the course that was found to be instructionally weak (C), a revised version of the course that had an improved instructional design (IB), and a version of the course that was exactly the same as the PSI-P version, except that feedback to the student was delayed (PSI-M). Students enrolling in Introductory Accounting at Athabasca University from September 1 to November 14, 1979, participated. Results indicated that the PSI model (PSI-P) produced higher completion rates than the other three versions. In addition, small differences were found between versions C and IB. Differences between the PSI-M and IB versions were minimal. No differences were found between any of the versions with respect to examination performance. Estimated cost data suggested the PSI-P version is two to three times more expensive to deliver than the other versions. A reason suggested for the higher completion rate of the PSI-P condition was that the PSI model has an instructional as well as a management system for dealing with students. (Seven tables and one figure are attached.) (YLB)