The lack of direct communication with the intensive care patient means the medical staff have to try to achieve a realistic picture of the condition of the patient from numerous pieces of detailed information fitted together something like a jigsaw. The immense amount of data thus gained means an overall interpretation of the many individual data would be hardly imaginable without the use of a computer. PC networks in conjunction with a high-level language provide an ideal basis for building up a background monitoring system that can be used at the bedside. Simple PC-ATs and software developed in house in Turbo-Pascal have enabled us to realize a useful and very economical computer-aided background monitoring system. Any online and offline data important for an operative critical care unit can be collected, documented, displayed and processed in secondary parameters.