The objective of I(2)Cnet (Image Indexing by Content network) is to provide network-transparent content-based access to medical image archives as an Internet/intranet value-added service. Through a typical web browser, healthcare professionals interact with image collections, browse images similar to a query image, compare these images to images from other collections, and contribute their own images or comments. Specific I(2)Cnet services available on the World Wide Web (WWW) include image processing and feature extraction, content- and annotation-based search for images and image-related information, and authoring of annotations and image descriptions. Virtual workspaces provide the necessary mechanisms to support user sessions in I(2)Cnet, providing for service interoperability, persistence, and user interaction. In the course of a user session, which begins with a workspace log-in and ends explicitly with a workspace log-out or implicitly by exiting the browser,virtual workspaces maintain the common context. (C) 1997 Elsevier Science B.V.