Postoperative convalescence after esophagectomy is frequently complicated by pulmonary insufficiency and a high mortality rate. The literature and our own observations suggest that pathological changes actually begin during the operative procedure; we therefore studied 11 male patients during and after esophageal surgery by monitoring heart rate, systemic and pulmonary arterial pressures, cardiac output, extravascular lung water (EVLW), cardiac index, and systemic (TPR) and pulmonary vascular resistance (PVR). Blood samples were taken for analysis of epinephrine, norepinephrine, serotonin, and arterial and mixed-venous blood gases. The changes were found to be most marked during esophageal resection: PaO2 decreased from 217 to 147 mmHg while PaCO2 increased, i.e. pulmonary gas exchange was disturbed (Fig. 4). PVR (Fig. 3) and mean pulmonary arterial pressure (MPAP) (Fig. 2) increased after esophagectomy. Norepinephrine, but not epinephrine (Fig. 6), increased continuously until the end of the operation. EVLW was slightly elevated at approximately 9 ml/kg body weight before operation and did not change during surgery. Six patients who developed severe pulmonary complications showed lung water retention up to 18 ml/kg body weight on the 4th postoperative day (Fig. 5). Compression of the heart and lungs as well as injury of the vagus nerve during esophagectomy may provoke increased MPAP, PVR, and disorders of pulmonary gas exchange. Furthermore, the non-respiratory function of the lung must be taken into consideration: the lung is known to have clearance activities for various endogenous substances such as norepinephrine, serotonin, some prostaglandins, and bradykinin. Most of these substances may provoke vasoconstriction followed by disturbances of microvascular permeability and gas exchange in the lung.(ABSTRACT TRUNCATED AT 250 WORDS)