Description of medical information systems at various levels of organization. This paper traces the history of biomedical data processing and outlines primary sources of difficulty for R&D, including technological design and instrumentation, cross-disciplinary communication, clear task formulation, and modeling problems. The challenge for information system technology, in a patient-management decision problem, for example, is to convert data to functional, on-line information having utility in a medical context. Although it may be sufficient, perhaps, simply to move the data from place to place and list it at the output, copying the manual methods, this would not exploit the real value and potential of the computer system. There are many other cases in which the computer can be used to support the decision process: sophisticated patient monitoring, image processing and pattern recognition (as in EKG analysis), prediction of drug effects, fully automated mass screening, and lay education. 68 pp. Bibliog.