Collaboration among healthcare organizations depends on coordination, communication and control among healthcare organizations and effective sharing of medical information and knowledge. Medical services are knowledge-intensive activities. All information, knowledge, techniques and experience should be integrated, managed and shared using the Internet and information technology. Overall medical service quality and efficiency would be improved markedly if medical professionals and staff at different healthcare organizations could use and share medical knowledge resources. Therefore, a collaborative medical knowledge service would promote medical service quality. This study presents a novel medical knowledge service system for cross-organization healthcare collaboration such that all medical professionals and staff at different healthcare organizations could capture, store, manage, integrate and share medical knowledge. This system should improve medical service quality and efficiency, and promote competition in the healthcare industry.