There has been a large amount of research on the relative effects of cooperative, competitive, and individualistic learning on achievement and productivity. This paper reports a study designed to determine the effect of cooperative learning strategies on mathematics achievement of 7th graders. Based on school records indicating whether a student had participated in the cooperative learning strategies group or had received individualized/competitive instruction, 50 seventh-grade students were selected from an elementary school located in a low socioeconomic neighborhood in Chicago made up of all minority students. Scores on the mathematics portion of the Iowa Test of Basic Skills administered in the Spring of 1991 and 1992 were utilized to compare the mathematics achievement of the students in the two groups. T-tests performed on the pre-test and post-test data indicated that no differences existed in the groups prior to instruction, but that the cooperative learning groups performed significantly higher on the post-test. These findings confirmed results of similar studies. The paper concluded that cooperative group learning strategies are more effective in promoting mathematics achievement. (MDH)