A prospective analysis was carried out on 19 adult patients who had undergone total gastrectomy for gastric cancer with truncular vagotomy and postoperative TPN, to evaluate the gallstone formation sequence in man. The patients underwent gallbladder ultrasonography before surgery, then at least once a day during the period of postoperative fasting and TPN (about 15 days) and during the first days after oral refeeding. No patients showed cholelithiasis or biliary sludge at preoperative ultrasonography; none showed cholesterol crystals at preoperative duodenal drainage. 10 of the 19 patients were sludge-positive during the first two weeks of TPN (2 after 3 days, 7 at day seven, 9 at day nine). 6 patients who were initially sludge-positive developed microlithiasis: 1 after 7 days, 2 during TPN and 3 after oral refeeding. These results lead the authors to suggest that human lithogenesis in particular conditions may be faster than that observed so far in animal models, and that the very rapid events in gallstone formation observed in this study concern the formation of pigment stones.