This research was concerned with the collection of empirical data necessary to estimate the effects of decision support tools on the performance of distributed groups. Data was collected in a controlled experimental environment that simulated a geographically-dispersed meeting through the use of videoconferencing and group communication support (GCSS) technology. Results of the use of a Group Decision Support System (GDSS) on group process and outcome variables were mixed. As predicted by the literature the use of a GDSS by distributed groups improved overall group consensus, decision accuracy, and decision effectiveness. The use of a GDSS also increased perceived process structure. Contrary to previous studies, the use of a GDSS increased decision time, and decreased overall satisfaction with the group process. No significant effects were found for perceived consensus, cooperation, amount of information exchange, or confidence in the decision. A strong correlation was found between decision quality and decision time. An even stronger correlation was found between perceived structure of the process and satisfaction with the process. The lack of feedback about the process and its outcomes could explain the lack of a GDSS effect on perceptions of consensus, cooperation, and confidence in the decision. Perception of subjective measures of the process may depend on the presence of the appropriate types of feedback. The results suggest that an increase in structure without a perceived improvement in decision quality (confidence in the decision) tends to reduce group satisfaction. A richer taxonomy for Computer Supported Cooperative Work (CSCW) systems is proposed whereby three orthogonal dimensions of group support are defined. These three dimensions of group support are: Communication support, decision support, and presence support. This new taxonomy suggests a number of research directions aimed at the empirical identification of contextual and design factors relevant to distributed group performance and decision making performance in general. / Master of Science