This is non-randomized phase 2 study to evaluate toxicity and efficacy of valproic acid (VA) with concurrent chemoradiotherapy (CCRT) containing weekly gemcitabine in patients with unresectable locally advanced pancreatic cancer (ULAPC). All patients will be planned for three-dimensional conformal radiotherapy (3-DCRT). A total dose of 54 Gy will be delivered using 2 Gy daily fractions given over 5 days a week.Intravenous (i.v.) chemotherapy (ChT) with gemcitabine 300 mg/m2 will be started at the first day of 3-DCRT.Total 5-6 weekly doses of i.v. ChT will be planned.VA will be administered orally in daily dose of 800 mg. Treatment with VA will be commenced at the first day and will be terminated at last day of RT.The patients will be followed till disease progression or death.