The Extra Vascular Lung Water (EVLW) was measured using the thermal sodium double indicator dilution technique in 21 patients undergoing surgery for esophageal cancer. This measurement is an important parameter in the control of the respiratory function. In the 16 cases without pulmonary complications, the preoperative EVLW was 5.3 +/- 0.2 (mean +/- SEM) ml/kg and the immediate postoperative EVLW was 4.8 +/- 0.4 ml/kg. This change was significant (p less than 0.05), but within 24 hours the EVLW returned to almost the same levels as those recorded before surgery. In only 3 cases, the EVLW were elevated beyond 7.5 ml/kg, but these high EVLW levels did not continue for more than 12 hours. Of the 5 patients with pulmonary complications, only two experienced pulmonary edema. Their preoperative EVLW levels were normal, but the immediate postoperative EVLW levels were significantly elevated beyond 10 ml/kg. These elevated levels were observed before the PaO2, the portable chest roentgenograms and the other test results changed following surgery. The high EVLW levels beyond 7.5 ml/kg continued for 72 hours after surgery. We found no correlation between the EVLW and measureable hemodynamic parameters (Cardiac Index, Pulmonary Wedge Pressure, Colloid Osmotic Pressure-Pulmonary Wedge Pressure gradient) during the observation period. In the other cases with pulmonary complications (2 cases were pneumonia, one was atelectasis with pneumonia), the changes in the EVLW levels were the same as for the cases without pulmonary complications. These results indicate that the EVLW is the optimum parameter for the control of the respiratory function and early diagnosis of pulmonary edema after surgery for esophageal cancer.