Designed as an introduction to a symposium on the appropriateness of mastery learning as a technique of social studies instruction, this paper reviews research on the variables related to mastery learning in order to provide a basis for systematic symposium discussion. Brief research reviews are included on the following variables: materials, instructional procedures, criteria for mastery, teacher characteristics, pupil characteristics, classroom environment, duration of mastery sequence, and management problems. Appendix A contains a more extensive list of variables for further discussion, and Appendix B indicates a hypothetical and cumulative research sequence which is necessary to establish a body of reliable knowledge about mastery learning. Brief reviews of the four research studies which were presented at the symposium are included in Appendix C. A bibliogrpahy of related research on mastery learning is also included. (DE)