The routine use of an arbitrary fixed left atrial (LA) pressure during volume load after aortocoronary bypass operation was compared with use of an individualized postoperative target LA pressure according to a calculated preoperative LA pressure in two groups of consecutive patients. The preoperative LA pressure of each patient was calculated from the preoperative left ventricular end-diastolic pressure (LVEDP) by the formula: mean LA pressure = 1.16 x LVEDP - 8.53. Left atrial pressure, mean arterial pressure, mean right atrial pressure, and cardiac output were measured simultaneously on arrival at the intensive care unit and 60 minutes later. Cardiac index (CI) and systemic vascular resistance (SVR) were calculated from the variables already mentioned. Results indicated a significantly higher CI and significantly lower SVR in patients in whom volume load was aimed at the calculated preoperative LA pressure. It was concluded that the optimal postoperative LA pressure is specific for each patient and depends on the preoperative LVEDP.