In the present study a statistical monitoring method used in industrial process control has been adapted to monitor physiological and pharmacological responses in an intensive care environment. The limitations of the basic technique have been overcome with the development of a modified signal called the Patient Condition Factor. With this development the identification of improvement or deterioration in a physiological variable alerts the clinician to the possibility of an alarm state before the preset limits of an acceptable range are reached, while attributing identical significance to similar fundamental changes in the measure of a variable. The various parameters which are derived are output, along with the absolute value of the variable, to an on-line real-time visual display terminal in the operating theatre. This not only results in a totally objective measure of physiological trend but assists the clinician in his interpretation of the patient's condition, thus extending the detailed management of the intensive care state.