Uptake and excretion of intravenously injected I131-tagged rose bengal is detected by a scintillation counter directed at the liver. The record of liver activity versus time is analyzed graphically to obtain 3 constants[long dash]uptake halftime, excretion halftime and liver blood pool. In hepatocellular disease, both uptake and excretion are slow; in obstructive disease excretion is more delayed than uptake. Data is presented to illustrate the usefulness of the test in differential diagnosis of liver disease.