Of 176 patients with carcinoma of the pancreatic head region 156 underwent standard pancreatoduodenectomy (group 2) and 20 with macroscopic suspicion of invasion of the portal vein or superior mesenteric vein (SMV) underwent pancreatoduodenectomy with partial resection of the portal vein or SMV (group 1). In 16 patients in group 1 end-to-end anastomosis was used for reconstruction of the vein. The morbidity rate in groups 1 and 2 was similar (55 versus 63 per cent). The hospital mortality rate was 15 per cent in group 1 and 7 per cent in group 2 (P = 0.22). Histological examination confirmed tumour invasion of the portal vein or SMV in ten patients in group 1. Invasion of the portal vein or SMV was significantly more frequent in patients with pancreatic cancer than in those with distal bile duct or ampullary carcinoma. Of the 20 patients in group 1 only three underwent curative resection with tumour-free margins. The median survival time after resection of the portal vein or SMV was 8 months; the 2-year survival rate was 19 per cent. Comparison of survival in group 1 with survival in subgroups of patients undergoing standard pancreatoduodenectomy, matched for all histological parameters, showed no significant difference. It is concluded that partial resection of the portal vein or SMV in patients undergoing pancreatoduodenectomy who are suspected of having tumour invasion of the portal vein or SMV does not improve either the rate of curative resection or survival.