Eleven patients underwent surgery with central venous pressure (CVP) and pulmonary artery (PA) pressure monitoring. In operations with minor blood losses, PA pressure was stable except for transient peaks at the times of incision and extubation. In patients who had both prior evidence of heart disease and operations with large volume losses, PA end-diastolic pressure (PAEDP) was a more sensitive and reliable index of circulatory overload. Levels of PAEDP compatible with pulmonary edema were recorded despite normal CVP values in several such patients. Patients with heart disease had higher mean PAEDP and wider variation of PAEDP for any given CVP value, emphasizing the value of PAEDP in detecting discrepancy between right and left ventricular performance. Evidence of heart disease in patients who need large volumes of fluids is a sound indication for PAEDP or wedge pressure monitoring.