This is a Phase I trial of gemcitabine given weekly as a 30 minute infusion administered concurrently with radiation in patients with locally advanced or locally recurrent pancreatic carcinoma. Patients will be treated with external beam radiation therapy in a standard manner. Gemcitabine will be administered as a 30 minute infusion beginning on the first day of irradiation and weekly afterwards for a total of 5 doses. Patients will be assessed clinically for acute toxicity which will be graded per RTOG and DCT toxicity grading system.