Mastery learning is both a philosophy about student learning and a set of instructional implementation techniques. This volume presents 10 case studies of instructional programs identified as mastery learning or outcome-based education. The programs are organized according to whole-class mastery, flexible grouping, flexible grouping/continuous progress, and continuous progress approaches. Also included is a case study of an instructional management program. None of these programs was found to comply fully with program models described in the educational literature. This is not surprising, since the translation of outcome-based ideas within a time-based school organization structure is bound to yield imprecise results and compromises. The last chapter reviews the 10 sites and outlines some program and maintenance issues. The first section discusses seven obstacles to program implementation and maintenance. The final section presents a general design for implementing any of the instructional organization models. Two fundamental activities are involved: (1) establishing a mastery-oriented belief system; and (2) developing a comprehensive building level plan for program implementation and support. A description of the case study methodology and the survey instruments are appended. (44 references) (MLH)