The problem of this study was to determine whether Kenyan Bible college students who receive instruction using a modified (highly structured) mastery learning model will demonstrate greater achievement in knowledge of Christian Church history as compared to Kenyan Bible college students who receive instruction using a traditional (minimally structured) non-mastery learning model. The subjects were 17 second-year Kenyan Bible college students enrolled in a course on Christian Church history, and they were randomly assigned to the two treatment conditions. The researcher served as instructor for both groups. The experimental group used a textbook, detailed syllabus, 200 page study guide (featuring an advance organizer to provide an ideational scaffolding), and a lesson-development feature (providing an enabling objective, congruent questions, and informative feedback for each lesson segment). The control group used a textbook and a less-detailed syllabus. Both groups shared the same classroom lectures, class discussions, required assignments, examinations, and review of examination items. Five tests of Christian church history were administered, including a pretest, three unit tests, and a comprehensive course examination. Test data were analyzed using a 2 x 5 (treatment x testing occasion) repeated measures analysis of variance (RM ANOVA). The percentage of students performing at mastery level (80% correct) on each test was also calculated. Results indicated that, from the second unit test to the comprehensive examination, the modified mastery learning group achieved slightly but consistently higher mean percentage correct scores than the traditional group, but there was no significant main effect for treatment. In contrast, the main effect for testing occasion did reach statistical significance. Across the five test occasions, 8% to 51% more students in the modified mastery learning group attained mastery level as compared to the traditional learning group.