It is argued that computer assisted instruction might be an answer to the scheduling problems resulting from the implementation of mastery learning programs in the public schools. The mastery learning model proposed by Carroll and the transformation of this model into a working model by Bloom are described. The difficulty of implementing mastery learning given the fixed schedules of public schools is noted, and the potential contribution of computer assisted instruction (CAI) is outlined, noting that CAI facilitates instruction at the student's own pace while reducing constraints on teachers' time and allowing them to devote more time to students requiring remedial instruction. Criteria for instructional software which can support mastery learning are outlined. It is noted that software must be clear and understandable; must motivate students actively in drilling subject matter, passively in reinforcing all learned subject matter, and interactively to give fast, positive feedback; must move consistently through subject matter and end at a given mastery level of objectives; and must be both user-friendly and entertaining. Emphasizing that the computer cannot replace the teacher or the textbook, the paper concludes with a model for CAI use in mastery learning situations which incorporates initial teacher instruction, student practice (individually and in groups), formative testing, teacher remediation and CAI lesson referral, CAI (paired or with small group practice), further teacher remediation, and summative testing. (5 references) (GL)