Extravascular lung water (EVLW) was measured at the bedside in 12 patients with the thermal-green dye double indicator dilution method using a microprocessor. The EVLW ranged from 3.3 to 17.2 ml/kg body weight; in patients without pulmonary problems we have found an average EVLW of 5.7 ml/kg body weight. The method involves easy calculations and is reproducible and accurate.