Between 1970 and 1987 valvular operations with cardiopulmonary bypass were performed on 636 patients, with an overall early mortality of 7.5%. To determine the critical indication for valvular surgery, preoperative clinical characteristics were examined by comparing 35 patients, who had died of surgery because of low cardiac output syndrome or multiple organ failure, with operative survivors. The multivariable logistic analyses demonstrated that NYHA functional class IV, multiple valvular disease, large CTR more than 70%, high left ventricular end-diastolic pressure more than 15 mmHg, depressed left ventricular ejection fraction less than 40%, and renal and hepatic dysfunction were powerful independent clinical characteristics concerning operative mortality. The mortality was highly significant when a patient was associated with more than three of the above factors in addition to being NYHA class IV. It should be emphasized, however, that there are three survivors among 11 patients with all six factors. On the other hand the prognosis of such patients without surgery was very poor, fifteen of 21 patients, medically treated during the same period, died within two years after reaching NYHA class IV condition. These results show that several predictors are useful for decision making regarding the indication for valvular surgery. Surgery, however, should not be denied because of the severity of the disease.