The author uses concepts of social psychology to examine "learning-by-tutoring" tutorial projects designed to enhance the learning of both tutors and tutees by ensuring that tutors are teaching work that they themselves need to practice. Selected areas of social-psychological research are briefly described, and concepts from these areas are applied to tutoring projects. Effects that are widely reported for tutoring projects are shown to correspond to reasonably well established social-psychological processes, and theories from areas of social psychology are shown to predict effects that have not been reported in the literature on tutoring or by practitioners. Using these two approaches the author identifies a number of topics needing empirical testing: (1) main attitudinal effects of the role of tutor; (2) long-term effects of the role of tutor on cognitive functioning; (3) effects of tutoring on social relationships; (4) social effects of tutoring on groups; (5) aptitude treatment interaction and the role of tutor; (6) effects of tutoring on teachers' expectations; (7) training of teachers and tutors; (8) process studies of bases of influence; (9) formative evaluation; (10) the question of payment of tutors; and (11) process studies of influences on tutees. (MJB)