We have developed, as a pilot project, a hypertext-based reference system for anesthesia in a neurosurgical clinic. The intention is to give passive decision support prior to the operation. The information is presented according to the different needs and knowledge levels of the anesthesiologists. Therefore, with the aid of a simple and universal user interface (mouse and screen keys, no keyboard) the information is structured from basic to more detailed information. To complete the operation-related material the system also offers relevant data from the "anesthesia-related background knowledge" (pre-existing diseases, drugs, and medication, etc.). As an example, a short path through the system is shown to illustrate the presentation and linkage of information.