A study of the key wordings used by the doctors in medical records in ICU preceded this implementation; they constitute a thesaurus (2700 strings) organized in 2 trees. These strings are proposed along the dialogue which occurs between the microcomputer and the user; on these bases, several graphs allows movement in the tree by minimization of the pathway. The use of the thesaurus with the corresponding graphs necessitates only one automaton program. This medical data microcomputerized system is transparent for the user, thanks to a multilayered software. In the external layer the microcomputer provides access to the system by one of the following function keys: creation of a medical record, additional information on a medical record already known, research of a medical record, listing of the open medical records, printing of a medical record. Each one of these function keys provides access to the following 5 chapters: identity, antecedents, reasons for admission, evolution, destiny; these chapters use parameterized procedures. This software is implemented on a low-cost microcomputer fitted with a dual drive disk (170 kilobytes each) and a printer (90 characters/s).