Reviewing research on grade retention, this paper describes tools and guidelines developed as an aid in retention decisions and examines actual promotion/retention policies and practices. Most research on academic and social effects of grade retention suffers from poor methodology, leaving the conclusions suspect and the results contradictory. The research designs are divided into three types; two are biased for or against retention, while the third type is the only effective design comparing the value of retention and promotion. Unfortunately, only three studies used this design type and all had additional problems. The review of research indicated that: (1) grade retention may be beneficial for a small number of students, but it does not seem to help most students; (2) the value of retention in improving academic achievement of low-achieving students depends on the criteria used; (3) retention does not harm self-concept; (4) repeating a school year is related to poor social adjustment and increased likelihood of dropping out; (5) retention does not appear to effectively motivate low-achieving students; and (6) primary grade students with good social/emotional adjustment who are low achievers benefit most from retention. Promotion/retention policies should be flexible and allow for individualized decisions. (MD)