This journal issue addresses the topic of mastery learning at both the elementary and secondary school levels. The first article, "The Theory and Practice of Mastery Learning" (Guskey), gives a definition of and information about the development, operation, and application of mastery learning, based on the theories of Benjamin Bloom. In addition, the article addresses common concerns about mastery learning and implications for teachers. "Mastery Learning: Its Prospects and Problems" (Horton) identifies six basic components of mastery learning (objectives, preassessment, instruction, diagnostic assessment, prescription, and postassessment) and discusses associated implications and problems. In the third article, "Mastery Learning: Some Suggestions for Implementation" (Shanes), ideas for orientation, enrichment activities, and classroom management are given. Sample letters to parents and students, a glossary of mastery learning terms, and sample enrichment activities are also provided. The final article, "Mastery for Higher Cognitive Thought Processes: Is It Possible?" (Killoran, Zimmer, and Fischer), discusses the construction of tests for higher cognitive thought processes and provides three examples of tests, correctives, and retests. (LH)