This paper describes a computerized system for the simultaneous monitoring of the electrocardiogram, atrial electrogram, pulmonary and systematic arterial pressures and thermodilution cardiac output. New features include techniques for atrial rhythm monitoring and for automated pressure and cardiac output measurements. Monitoring of the atrial electrogram, recorded via a modified Swan-Ganz catheter, permits a computerized analysis of atrial rhythms and atrioventricular conduction. The bedside hemodynamic equipment has been re-designed to provide simplified operation, disposable components, continuous pressure monitoring, automated cardiac output measurements and improved patient safety. Simultaneous electrophysiologic and hemodynamic monitoring is now used routinely for both clinical research and patient care. The ability to continuously monitor physiologic disturbances has significantly improved the physician's ability to recognize problems early and assess the response to therapeutic interventions.