Summary:Measurement of regional hepatic blood flow using radioactive xenon by Gelin's method was studied in 20 controls and 21 patients with primary carcinoma of the liver, eight of whom had associated cirrhosis. The mean value of blood flow for controls was 28.77±9.50 ml/min/100 g, for carcinomatous nodules 12.21±5.83, for normal areas in the liver with primary carcinoma 37.88±12.88 and for cirrhotic areas in the liver with primary carcinoma 21.50±10.16. The blood flow of carcinomatous tissue is significantly less than of normal parenchyma and this can be explained by the histopathological and angiographic findings. Temporary reduction in the blood flow was obtained by ligation of the hepatic artery and postoperative angiography demonstrated the formation of collateral arteries to the li