This study illustrates the local spread of lower bile duct cancer with thin-section helical CT in correlation with the surgical and pathological findings. Pathologically, 16 patients had pancreatic invasion, 4 had small bowel mesentery invasion, 7 had extrapancreatic nerve plexus invasion, and 3 patients had vascular invasion. On thin-section helical CT, pancreatic invasion was correlated to the clarity or non-clarity of the bile duct mass-pancreas border and the presence of an intrapancreatic mass. Cases with small bowel mesentery and extrapancreatic nerve plexus invasion showed mass or stranding around the superior mesenteric artery and/or inferior pancreatoduodenal artery. Vascular invasion was seen as tumor contiguity to these vessels.