Factors determining the prognosis of cancer of the pancreatic head were analyzed in 100 patients who had undergone surgical treatment. So as to clarify the indications for pylorus-preserving pancreatoduodenectomy (PPPD), the prognosis was compared in two sets of such patients, 25 who had undergone PPPD and 25 who had undergone the Whipple procedure. Of these 50 patients, 20 (40%) also underwent portal vein resection and 29 (58%) were found to have lymph node metastasis. Curative resection was achieved in 33 of these 50 patients (66%) and the 5-year survival rate after the curative resection (42.0%) was significantly higher in these patients that in those given a non-curative resection (P <0.01). Further, the prognosis was better for patients who did not require a portal vein excision than for those who did (P<0.01), and for patients who showed no lymph node metastasis than for those with metastasis (P<0.01). The 5-year survival rate did not differ significantly between the PPPD group and the Whipple procedure group. These results indicate that PPPD can also be a useful procedure for treating malignant diseases.