Résumé : A protein loading test was performed in nine disease free subjects and in ten patients suffering from liver disease. These studies were performed after an overnight fast. Subjects began the test by drinking 20 ml of water/kg body weight. Thereafter, urine volume was replaced with equal quantities of water. Baseline and postprandial GFR was calculated from the endogenous creatinine clearance since, in this test, it has been shown to be comparable to inulin clearance. The results of the protein loading test in the disease free group are shown. Creatinine excretion was significantly greater (P < 0.02) after protein loading than in the baseline period. Glomerular filtration rate behaved similarly (P < 0.05). In these subjects, baseline GFR and postprandial GFR averaged 114.1 ± 9.8 ml/min/1.73 m2 and 159.3 ± 20.8 ml/min/1.73 m2, respectively, with the latter value representing an increase of 40% over baseline. In the group of patients with liver disease, creatinine excretion and GFR were not different in the baseline period or after protein loading. Baseline GFR averaged 118.3 ± 10.1 ml/min/1.73 m2 and postprandial GFR was even lower, although not significantly so, at 102.6 ± 7.8 ml/min/1.73 m2. Individual values are shown in Table 1. As can be seen, baseline values were not different in the two groups. In the one patient tested during the acute phase of viral hepatitis, baseline GFR was 154.2 ml/min/1.73 m2 and test GFR showed no increase at 150.2 ml/min/173 m2. Two months later, after complete recovery as assessed by normalization of liver function tests, this patient displayed a normal test with baseline and postprandial GFR values of 124.5 and 154.8 ml/min/1.73 m2, respectively.