This paper presents WebOnCOLL, a web-based medical collaboration environment, which has been designed in the context of the regional healthcare network of Crete. WebOnCOLL employs the infrastructure of regional healthcare networks to provide integrated services for virtual workspaces, annotations, e-mail, and on-line collaboration. Virtual workspaces support collaborative concepts like personal web pages, bulletin boards, discussion lists, shared workspaces, and medical case folders. Annotations provide a natural way for people to interact with multimedia content, while e-mail is one of the most popular forms of communication today. On-line collaboration satisfies the need for a more direct form of communication.