beta-cell neogenesis is expected to provide a new therapy for diabetes. Numerous studies have demonstrated that transcriptional regulation involving pdx-1 is essential for endocrine neogenesis in vivo and in vitro. Therefore, it is possible that ectopic expression of pdx-1 in the pancreas could induce endocrine neogenesis. To test this possibility, we performed safe and efficient gene delivery of the pdx-1 gene into the mouse pancreas through the common bile duct using adenoviral vectors, and examined the effects of the ectopic expression of pdx-1. Here we show that adenovirus-mediated expression of pdx-1 can activate the endogenous pdx-1 gene, leading to beta-cell neogenesis and ductal proliferation. This technique is similar to the endoscopic retrograde cholangiopancreatography, which has been already established as a safe procedure for humans. Thus, beta-cell neogenesis induced by adenovirus-mediated expression of pdx-1 provides a novel strategy for gene therapy for a cure for diabetes mellitus.