Visceral radiocolloid angiography was performed in 1230 consecutive patients studied with scintigraphy of the reticuloendothelial system (RES). The hepatic arterial flow was considered increased if an early and obviously increased accumulation of the radiocolloid occurred in the liver during the visceral radionuclide angiography, i.e. that the early part of the liver time-activity curve coincided with the early parts of the kidney and spleen time-activity curves with respect to time and steepness. A generalized increase of arterial blood flow to the liver was found in 70 patients, of whom 54 per cent had alcoholic liver disease, 20 per cent metastatic liver disease, 19 per cent had various diagnoses, and in 7 per cent no certain diagnosis was found. Generalized increase of arterial blood flow to the liver gives a typical appearance in radiocolloid angiography and the corresponding time-activity curves. It may be a sign of severe disease, most often localized in the liver, but in some cases it may be of extrahepatic origin. In 27 per cent it was the only obvious pathologic finding. It was in a few cases a reversible condition. Generalized increase of arterial blood flow to the liver is a clinically important finding that could escape detection if radionuclide angiography is not included in the RES scintigraphy.