Knowledge engineering should meet the users, that is, physicians, nurses and other health care providers. They all handle natural language medical texts. Natural Language Understanding is thus a rapidly growing field of direct concern to medical informatics. Its potential for tomorrow's applications is important although it is limited by its ability to ground its components on a solid model of the domain. This paper considers the benefit of a closed connection between a semantic network modelling a medical domain, and a Natural Language Understanding system working in this same domain. It overviews a number of natural language applications foreseen in the future and provides some recommendations about the future use and benefits of natural language techniques.