Distributed group support systems are likely to be widely used in the future as a means for dispersed groups of people to work together through computer networks. They combine characteristics of computer-mediated communication systems with the specialized tools and processes developed in the context of group decision support systems, to provide communications, a group memory, and tools and structures to coordinate the group process and analyze data. These tools and structures can take a wide variety of forms in order to best support computer-mediated interaction for different types of tasks and groups. This article summarizes five case studies of different distributed group support systems developed by the authors and their colleagues over the last decade to support different types of tasks and to accommodate fairly large numbers of participants (tens to hundreds). The case studies are placed within conceptual frameworks that aid in classifying and comparing such systems. The results of the case studies demonstrate that design requirements and the associated research issues for group support systems an be very different in the distributed environment compared to the decision room approach.