Mizuno (2000) devised a spaced learning method, the Low-First Method, based on psychological findings related to spacing effects, for learning simple nonhierarchical materials and demonstrated its effectiveness in a CAI system. Then Mizuno (2001) modified it to be adaptive to individual differences of memory span, verified its effectiveness, and called it the Modified Low-First Method. However, in an evaluation survey (Mizuno, 2002b), a CAI system with the Modified Low-First Method was evaluated badly with respect to its facility of learning because it was hard for learners to monitor their progress. So, in this study, an experiment and a survey were conducted to demonstrate the validity of appending a multimedia mastery feedback device to the CAI system with the Modified Low-First Method to enable them to monitor their progress. The results indicated that mastery feedback enhanced not only the effectiveness and time-efficiency of the CAI system but also the evaluation of facility of learning as well as learners' motivation. Finally, the relationships between mastery feedback and metacognition and between multimedia and motivation are discussed.