PURPOSE: We conducted a phase II trial to assess the outcomes of patients who received preoperative gemcitabine-based chemoradiation and pancreaticoduodenectomy (PD) for stage I/II pancreatic adenocarcinoma. PATIENTS AND METHODS: Eligible patients with pancreatic head/uncinate process adenocarcinoma and radiographically defined potentially resectable disease received chemoradiation with 7 weekly intravenous (IV) infusions of gemcitabine (400 mg/m(2) IV over 30 minutes) plus radiation therapy (30 Gy in 10 fractions over 2 weeks). Patients underwent restaging 4 to 6 weeks after completion of chemoradiation and, in the absence of disease progression, were taken to surgery. RESULTS: The study enrolled 86 patients. At the time of restaging, disease progression or a decline in performance status precluded 13 patients from surgery. Seventy-three (85%) of 86 patients were taken to surgery, extrapancreatic disease was found in nine, and 64 (74%) of 86 underwent a successful PD. Median overall survival (86 patients) was 22.7 months with a 27% 5-year survival. Median survival was 34 months for the 64 patients who underwent PD and 7 months for the 22 unresected patients (P < .001). The 5-year survival for those who did and did not undergo PD was 36% and 0%, respectively. CONCLUSION: Preoperative gemcitabine-based chemoradiation followed by restaging and evaluation for surgery separated the study population into two different subsets: patients likely to benefit from PD (n = 64) and those in whom surgery would be unlikely to provide clinical benefit (n = 22). Furthermore, the encouraging overall survival observed in this large trial supports the continued investigation of gemcitabine-based preoperative therapy in resectable pancreatic cancer.