This paper gives an introduction to the teleradiology system MEDICUS which has been developed at the Deutsches Krebsforschungszentrum (German Cancer Research Center) in Heidelberg, Germany. The system is designed to work on ISDN lines as well as in a local area network. The global software architecture is explained in the article. Special attention has been given to the design of the user interface and data security, integrity and authentication. The software has been evaluated in a field test in Germany at 15 radiology departments in university clinics, small hospitals, private practices, and research institutes. First experiences show that the system is easy to use and can save time, patient transports and reduce film costs. It is well suited for remote consultation or for sharing resources, such as expensive equipments or radiologists.