A local area communications network (LACN) has been implemented successfully at the University of California, San Francisco (UCSF) Hospital. This technology, developed by the Applied Physics Laboratory of the Johns Hopkins University, facilitates communication among systems previously considered "incompatible". The implication of this experiment is that a modular, evolutionary approach to medical systems will soon be a viable alternative to the "total" single-vendor approach now commonly used. Substantial preparation by a medical center, however, will be required in order to use an LACN properly. This will probably be done in many cases with the assistance of a new type of medical systems vendor, i.e., one having no systems of its own to sell.