An Asynchronous Learning Network (ALN) is a Computer-Mediated Communication System designed to support "anytime/anywhere" interaction among students and between students and instructors. A field experiment compared groups and individuals solving an ethical case scenario, with and without an ALN, to determine the separate and joint effects of communication medium and teamwork. Dependent variables include quality and length of the reports, and subjective perceptions of learning and satisfaction. The results indicate that that an ALN enhances the quantity and quality of the solutions to an ethical case scenario. The combination of teamwork with ALN-support increases the students' perception of learning. Although the perception of collaborative learning was similar between ALN-supported and unsupported groups, participants in computer-mediated groups reported lower perceptions of discussion quality than participants in manual groups.