In 96 patients with unquestionable pancreatitis the hourly excretion of amylase in the urine was determined on the basis of a 2-hour collection of urine. The values obtained were compared with the values for serum amylase and, in some instances, for serum lipase. The value for serum amylase exceeded the upper limit of normal in only 36% of tests, while the value for urinary amylase exceeded this limit in 74% when both were determined on the same day. When these two tests and the serum-lipase test (all three performed on the same day) gave increased values, the mean values exceeded the upper limit of normal 80% for serum lipase, 120% for serum amylase, and 710% for urinary amylase. Early, when the disease process clinically seemed more acute, the values for serum and urinary amylase were higher than normal in 53% and 78% of tests respectively, as compared with 15% and 54% later, when the acute process had largely subsided. Our observations, therefore, confirm those of earlier investigators that the urinary-amylase test is a much more sensitive reflector of the presence of pancreatitis and of its clinical course than is the serum-amylase or serum-lipase test.