We have evaluated the incidence and evolution of sludge, microlithiasis and lithiasis formation of the biliary tract in 12 patients who underwent total gastrectomy and postoperative total parenteral nutrition (TPN) beginning immediately after operation. To this end, serial ultrasonographic studies are carried out every 72 hours during TPN and every seven days after oral refeeding and then once a month for three months. Sludge of the gallbladder was demonstrated in five of the 12 patients after a minimum period of nine days after the operation, and in four of these, microlithiasis of the biliary tract was subsequently revealed. In two of these four patients, the stones dissolved spontaneously, while in the remaining two patients, no change occurred in dimension after intervals of six and seven months, respectively. In all instances, sludge and microcalculi were completely "silent." This study was done to underline the high incidence of biliary tract sludge and microlithiasis in the patients examined and to indicate the necessity for preventive measures against the possible and serious complications of this disease as well as acute pancreatitis.