The realization of the German law for a new structure of health care delivery by the ensurance of efficient structures and processes in hospitals calls for an optimal design of informational processes. To realize applications near to the users and just in time as well as to build up the complex functional relationships between departments and subsystems in big hospitals, a new design for Hospital Information Systems (HIS) is necessary. The features of modern HIS outlined in the paper can only be established by open systems, which guarantee portability, scalability and interoperability. This is also true in regionally distributed systems like the tumour register at Cancer Centres. In the paper the necessity and possibilities of open systems and different levels of application integration are discussed. The general statements are illustrated by practical realizations in the HIS of the Magdeburg University Hospital as well as in the tumour register at the Cancer Centre of Magdeburg/Sachsen-Anhalt. The creation of integrated structures for communications makes great demands on the ensurance of data security and data protection, especially for the inclusion of external partners from the region. In the context of high sensitive data of cancer patients data protection is of top priority. The legal problems of data collection, data storage and exchange in medicine are discussed first. The paper presents some aspects of the concept for data security and data protection in the Magdeburg University HIS and of the related concept for data protection in the tumour register of the Cancer Centre Magdeburg/Sachsen-Anhalt. Appropriate steps of realization are demonstrated. The application of hardware based modem access control systems with integrated encryption of data follows. The statements are extended to the planned installation of hardware based network access control systems with integrated encryption of data in the LAN.