Although duct-to-mucosa pancreatojejunostomy has been considered safer than other techniques, this procedure is particularly difficult when the pancreatic duct is small. It has therefore become increasingly necessary to develop a simple mucosal sutureless pancreatojejunostomy technique to replace the conventional hand-sewing one. Two hundred fourteen patients who underwent mucosal sutureless pancreatojejunostomy were classified into two groups: those with a normal pancreatic duct diameter (less than 3 mm, n = 97) and those with a dilated pancreatic duct (3 mmor greater, n 5 117). The rate of clinically significant pancreatic fistula (Grade B or C by the International Study Group on Pancreatic Fistula definition) among the patients as a whole was 8 per cent. The overall incidence of pancreatic fistula was significantly higher in the patients with a pancreatic duct diameter of less than 3 mm than in those with a pancreatic duct diameter of 3mm or greater. However, the incidence of clinically significant pancreatic fistula did not differ between the groups (less than 3 mm, 11%; 3 mm or greater, 5%; P = 0.09). Grade C pancreatic fistula developed in one patient with a pancreatic duct diameter of less than 3 mm and in two with a pancreatic duct diameter 3 mm or greater. Although two patients required reoperation, all of the fistulas were cured and the postoperative mortality rate related to pancreatoduodenectomy was zero. Mucosal sutureless pancreatojejunostomy combined with pancreatic duct stenting is associated with a low rate of clinically significant pancreatic fistula even in patients with a small pancreatic duct diameter less than 3 mm.