Howard, 1967).Following the demonstration that hepatic uptake of ICG is a saturable process (Hunton, Bollman, and Hoffman, 1961), Paumgartner, Probst, Kraines, and Leevy (1970) utilized classical MichaelisMenten enzyme kinetics to determine the maximal rate of ICG removal (Rmax) from disappearance rates of multiple, submaximal doses. The discovery of a close correlation between regenerating liver mass in the rat and Rmax by Rikkers and Moody (1974a) encouraged the application of this technique to the clinical estimation of hepatic reserve.The purposes of the present investigation are twofold: (1) to determine if hepatic removal of ICG in patients with chronic active liver disease follows saturation kinetics, allowing calculation of Rmax, and (2) to assess the role of azathioprine in the management of these patients by evaluating the influence of this drug on Rmax.