All uses of "Medical Data Processing", which make greatly divergent demands on the computer because of the different applications by different user groups, are to be considered from the points of view of hardware, software and organisation. Further possibilities for the complex information systems in the hospital arise from the more recent development of computer technology, also with regard to the reliability of the hardware. Hand in hand with this, an improvement in the system software can be seen for the real-time processing and time sharing. But organisation od design, planning, installation and operation is of particular importance for medical information systems. This also includes the preparatory training of the hospital personnel and the observance of data protection.