Whether bile spillage during operation presents a risk for peritoneal metastasis in the treatment of bile duct carcinoma was studied in 15 patients (12 with bile duct cancer, 3 with cancer of the papilla of Vater) who had all undergone a pancreatoduodenectomy. Preoperative bile was sampled through a percutaneous transhepatic biliary drainage catheter. Nine patients with bile duct cancer and one with cancer of the papilla of Vater showed positive bile cytology. The operative bile was obtained at the hepatic duct stump after a resection of the tumor-bearing bile duct. The operative bile in 10 patients with positive preoperative bile was found to be positive, while that in the five patients with negative preoperative bile was negative. Thus, the specificity of operative bile was identified as 100%. Moreover, in five patients with preoperative positive bile, saline irrigation of intrahepatic bile duct after a full recovery of hepatic bile revealed cancer cells to remain in the intrahepatic biliary trees. The viability of preoperative bile was 61%-97% with 1 x 10(4)-2.4 x 10(5) tumor cells, whereas there was a 41%-97% viability with 7.6 x 10(4)-10.4 x 10(5) tumor cells in the operative or irrigated bile. Accordingly, the patients with preoperative positive bile are thus suggested to be at high risk of inducing peritoneal metastasis due to the inadvertent spillage of hepatic bile at the time of resection of a bile duct tumor.