The early, accurate, differential diagnosis of jaundice frequently presents so much difficulty as to remain a source of concern. To carry out a surgical procedure in the presence of jaundice due to hepatocellular disease is as undesirable as permitting biliary obstruction to go unrelieved during a prolonged period of medical investigation. Despite the recent advances in the understanding of hepatic physiology and the increasingly sophisticated studies of liver function now available clinically, diagnostic acumen in this area has not been substantially enhanced. In 1931, Watson suggested that direct measurement of bile pigment in the feces of jaundiced patients might serve to identify those with biliary obstruction.4 It was his thesis that only the high-grade obstruction, such as that due to malignant disease, would completely prevent the arrival of bile pigments in the gastrointestinal tract. Although his studies have not been refuted, very few investigators have been persuaded to press