This paper reviews findings from over 70 published studies investigating various facets of learner-control in computer-based instruction (CBI). General conclusions about the relative effectiveness of learner-control versus program-control are equivocal. Across these studies, however, are strong suggestions that individual learner differences can greatly contribute to both the choices students make and to the effectiveness of those choices. Some researchers examine those differences on a global level, interacting with such broad instructional variables as learner-control versus program-control, following an aptitude-treatment interaction paradigm. Other investigators, however, look for interactions occurring on a moment-by-moment basis under micro-instructional conditions, that is the task-specific situation encountered during the course of the lesson delivery. Other paradigms are also discussed. The review extends the previous surveys of Carrier (1984), Hannafin (1984), Milheim and Martin (1981), and Steinberg (1977, 1989), paying particular attention to the role of learner individual differences in the effectiveness of learner-controlled CBI. Specifically, the impact on learner-control effectiveness of both rational-cognitive processes and emotional-motivational states of the learner are highlighted. Useful instructional prescriptions are proposed which take into account these variables. Recommendations for future research are offered. (Contains 188 references.) (Author/KRN)