Based on the concept that teachers can help students become better learners, mastery learning involves the identification of specific segments of learning and then mastery of them by individual students. Mastery learning provides a structure for teaching that includes class instruction followed by small group work. It is a group-based approach to individualized instruction in which students often can learn cooperatively with their classmates. Mastery learning is a way to individualize instruction within the framework of a traditional group instruction classroom setting. The mastery learning instructional model described in this publication involves four steps: (1) teaching the unit to the class; (2) giving a test to check students' learning at the unit's end and then assessing mastery of subject matter; (3) giving either enrichment activities or corrective activities to students as required; and (4) giving a second test to measure mastery again. This handbook also provides sample mastery learning units and answers to frequently asked questions about the mastery learning steps. (JMK)