Increasing complexity in medicine has caused clinical trial experts with disparate backgrounds from multiple organizations to collaborate when developing clinical trial protocols. Although many protocol-authoring tools provide computerbased decision support to assist in protocol writing, few of them provide sufficient collaboration support for a group of protocol writers. The iterative group writing activities among interdisciplinary clinical trial experts call for advanced tool support. Here we present a web-based protocol writing system with integrated support for collaborative reviewing and collaborative editing. The system uses a shared database to store threaded review comments and version information for electronic protocols. It also captures rich group event information to provide cross-activity awareness and to facilitate self-coordination within the collaborative writing team. We believe that our system can help streamline collaborative clinical trial protocol writing processes.