The recent arrival of portable computer systems with high-level language interpreters now makes it practical to rapidly develop complex testing and scoring programs. These programs permit undergraduates access, at arbitrary times, to testing as an integral part of a mastery learning strategy. Effects of introducing the computer were studied by using, for control, data from students enrolled in the same undergraduate educational pyschology course during the previous year. Results show that computer organized testing allowed students to take more replicates of each examination. Consequently there was, for three out of five examinations, an increase in the values of a measure of achievement based on the highest grade attained and time required before taking the final replicate desired for each examination of the course. Results of a student opinion survey indicated that in the presence of the computer organized testing, there was a greater feeling of learning than in a paper-and-pencil testing situation which allowed similar feedback with an invisible ink answer sheet. It was concluded that the feasibility of practical program development and that individual student utilization of portable, stand-alone, computer systems which now permit variable-paced mastery learning are propaedeutic in curriculum reform. (Author)