A new method has been developed which quantitatively assesses the relative arterial and portal venous blood flow in both normal and diseased liver tissue. Using a standard dedicated computer and routine clinical programs, the hepatic blood flow time/activity curve was analyzed. Specific indices were calculated: alpha1 represents aortic blood flow; alpha2, portal blood flow; alpha1/alpha2, the ratio of arterial to portal blood flow; and delta T, the difference in time between the peak of the arterial curve and the junction of the arterial and portal phases of the hepatic curve. Student's t-tests showed that these indices may be used to differentiate between the normal population and patients who have metastases or moderate to severe hepatocellular disease. Patients with early hepatocellular disease could not be differentiated from the normal population, but they could be separated from patients with more advanced hepatocellular disease. Patients with severe hepatocellular disease could not be separated from those with metastases. The most important uses of this technique may be in following a patient and determining when hepatocellular disease has become irreversible, and in following the course of treatment of a patient with metastatic disease to the liver.