Using analysis of variance and regression techniques, the authors analyzed the results of 40 studies that were conducted between 1953 and 1976 and contained 232 correlations between various measures of motivation and achievement. The motivation variables were restricted to students' achievement motivation, locus-of-control perceptions, and general as well as academic and mathematics self-concepts. Academic achievement was measured by ability or achievement tests or by grade point indices. The student characteristics studied included sex, grade level, and U.S. or non-U.S. location. The results indicated that motivation accounted for an average of 11.4 percent of the variation in academic achievement in the studies. Variation in the size of the 232 correlations resulted from the interaction among eight variables, including the nature of each study, the motivation or achievement measure used, and the grade level studied. Grade level, in fact, emerged as the only significant student characteristic, as students' achievement and motivation scores were more highly correlated in the later grades. (Author/RW)