The purpose of this study was to examine students' performance attributions for cooperative group assignments in a natural classroom setting. Three aspects of attributions were examined: (a) causal attributions made for performance outcomes on group projects, (b) perceptions of the underlying dimensions of causality, stability, and controllability of these attributions, and (c) the relationships among performance outcomes, attributional dimensions, and attributional consequences. The most typical attributions used for performance on the group assignment were effort, group strategy, group dynamics, situational factors, understanding of the task, motivation/attitude, nature of the task, and ability/prior knowledge. A factor analysis supported the dimensions of locus of causality, stability, and controllability for these attributions. As predicted by attribution theory, locus of causality was related to affective reactions and stability was related to expectancy for future success. The expected relationships for controllability were not found. © 1992.