Using 1025 junior secondary class three (ninth grade) students and twelve science teachers, this study investigated the effects of cooperative, competitive, and individualistic science laboratory interaction patterns on students' achievement in science and the level of acquisition of practical skills. A 3 × 3 (interaction pattern by ability) factorial model was employed for data gathering. Significant main and interaction effects were found for both dependent measures. The cooperative group was found to be superior on the achievement measure with no difference between the competitive and individualistic groups. The competitive group, however, outperformed the others in practical skills. Additional data indicated that the mixed ability cooperative group did significantly better than the mixed ability competitive group in achievement but not in practical skills. In sum these data are supportive of the differential effects of cooperative, competitive, and individualistic goal structures on cognitive and psychomotor tasks. Results are discussed in terms of their implications for more productive science laboratory work.