The purpose of this study was to investigate the relative effectiveness of positive interdependence and group processing on student achievement, interaction, and attitude in online cooperative learning. All of the participants, 144 college students enrolled in one of three different courses, received initial general instruction about teamwork skills and cooperative learning at the start of the study. Participants were then randomly assigned to one of three treatment groups: positive interdependence, group processing, and no structure. The ?positive interdependence? groups received subsequent positive interdependence skills training which were then utilized in their instructional activities. The ?group processing? groups received subsequent group processing skills training for use in their instructional activities. The ?no structure? groups received no additional instructional treatment beyond the initial basic teamwork and cooperative learning training. Results indicated that there were significant differences among students in the ?positive interdependence,? ?group processing,? and ?no structure? groups with respect to their achievement scores and interactions. Participants in the ?positive interdependence? groups had significantly higher achievement than participants in either the ?group processing? groups or the ?no structure? groups. In addition, participants in the ?positive interdependence? groups and the ?group processing? groups interacted with each other to a greater extent than those in the ?no structure? groups. This study also examined the relative effectiveness of positive interdependence and group processing on types of student interaction. The results indicated that ?positive interdependence? strategies were relatively more effective than ?group processing? strategies on ?sharing and comparing of information? interactions, whereas ?group processing? strategies were relatively more effective than ?positive interdependence? strategies on ?negotiation of meaning and co-construction of knowledge? interactions. Regarding student attitude towards the experiences of cooperative learning: participation, communication resources, and online activities, there was no significant difference among any of the three groups. The overall results of this study suggest that instructors would be advised to incorporate positive interdependence strategies in their online courses to help students perceive that they should actively contribute to their online group activities. In addition, instructors are recommended to inform groups of the individual progress of each member?s activities periodically by employing group processing strategies.