A randomized, controlled trial was conducted to clarify the effect of novel radiosensitizer, PR-350, accompanied by intraoperative radiology (IOR) on locally advanced pancreatic cancer. Between July 1999 and March 2002, 48 patients were enrolled in this clinical trial and received either PR-350 or placebo. Any differences between the PR-350 group (n = 22) and control group (n = 25) were not statically significant. All patients were evaluated, and none of them showed toxicity, with the exception of 1 patient from the control group, and the PR-350 compound was considered to be safe. The efficacy of IOR with PR-350 was evaluated using CT examination. The committee responsible for evaluating efficacy reported that 47.4% of the PR-350 group showed the effective response, compared with 21.7% of the control group (P = 0.1067, Fisher analysis). At 6 months following treatment, the tumor mass reduction rate in the PR-350 group was significantly improved (P = 0.0274). By the time of the last follow-up in July 2003, 17 PR-350 patients and 24 control patients group had died of the disease. The median survival period of the PR-350 group was thus 318.5 days and that of the control group is 303.0 days. One-year survival rates of the PR-350 group and control group were 36.4% and 32.0%, respectively. Although the PR-350 group did not demonstrate significantly better survival than the control group, 4 of 22 PR-350 patients were still living more than 2 years after the end of the trial, compared with only 1 of 25 patients from the control group. The mechanism of this increased therapeutic response to radiotherapy using PR-350 must be clarified to establish more effective strategy for pancreatic cancer treatment.