To support international medical collaboration activities carried out among Japan, Sri Lanka and other countries in Asia, we have been developing a collaboration system, which incorporates synchronous and asynchronous collaboration paradigms through network-effective persistent information sharing. The designed system facilitates synchronous collaborative work on maxillo-facial cases through real-time high-quality image delivery and by bringing the system database objects to a shared-workspace. The asynchronous activities are supported through a web based collaborative environment that enables both activity-centric and object-centric navigation of collaboration contents incorporated with email notifications of the system updates. Multimedia records of synchronous sessions are posted to the system database for later reviewing. Geographically dispersed groups experiencing different scales of network heterogeneities are served by a distributed application level multicast overlay and an adaptive multimedia delivery mechanism. The designed collaboration system also features several useful collaboration tools, user friendly GUI and ubiquitous connectivity.