Various kinds of collaborative systems have been developed to capture and represent individual rationales in shared group space with the firm belief that rationale sharing will benefit the group performance. Yet our understanding of the effects of rationale sharing in virtual group activities is very limited. As an initial step towards understanding the effects of rationale sharing on group processes, this study investigated the how one's awareness of the other group members' rationales affected the group processes in project-based virtual group activities. The findings suggest that one's rationale awareness promoted one's awareness of the other group members' expertise and contribution related to the group project. By organizing and managing the shared rationales in a dedicated group space, i.e., the shared rationale space, the group members' awareness of the others' contribution was supported. The results also suggest that the group developed its practice of managing the shared rationales and generating group rationales.