This paper proposes that "optimal flow," based on a cognitive theory of human motivation provides a useful measure of individuals' experiences as they participate in group work. Individuals' experiences of flow, a state of being characterized by involvement in and enjoyment of a task, were determined to be significantly greater in computer-mediated groups than in face-to-face groups. Variables associated with flow included perceived control, task challenge, and required skill during a problem-solving activity performed by fifty-nine undergraduate business students in both settings. The level of skill was found to be positively linked with perceived control in both face-to-face and computer-mediated groups. Perceived control in turn, was positively linked with the flow experience in both groups. Results indicate that while skill is important in explaining flow in the face-to-face task, the perceived challenge is important in explaining flow in the computer-mediated task. Suggestions are offered for future research on flow and computer-supported collaborative work.