Renal amylase clearance in relation to creatinin clearance (C_am/C_cr) was determined for 20 patients suffering from acute pancreatitis (AP). For each of them, the diagnosis rested upon operative or laparoscopic observation of characteristic anatomical or histological lesions. The average clearance relationship in these patients reached 16 ± SEM 3.8%. These results were significantly higher than those obtained from 132 patients who had been hospitalized for other medical or surgical diseases, as well as from 51 test patients (p < 0.001). The authors stressed the diagnostic importance of this test, in particular in the presence of a normal amylasemia level.