Introduction: Bioartificial pancreas (BAP) transplantation offers a potential treatment of diabetes mellitus. The optimal site for BAP transplantation has not yet been established. Aim: To monitor the effect of induction of neovascularization at the intermuscular space on islet survival after allogenic transplantation of BAR Methodology: Angiogenesis was induced at the intermuscular space of diabetic Lewis rats by implanting a polyethylene terephthalate (PET) mesh bag, which enclosed a collagen sponge and biodegradable gelatin microspheres containing basic fibroblast growth factor. After confirmation of angiogenesis, BAP was prepared by mixing of 5% agarose with approximate to2,800 isolated rat (Sprague-Dawley) islets and transplanted into the prevascularized PET mesh bag. Results: Neovascularization was observed in and around the PET mesh bag within 10 days after implantation as confirmed by macroscopic and microscopic examinations. In the presence of a collagen sponge, new blood vessels penetrated into the PET mesh bag and formed a vascular bed. After transplantation, normoglycemia was achieved in the rats within 3 days and maintained for >35 days. The rats gradually gained body weight, and the results of intravenous glucose tolerance test showed normal patterns of blood glucose clearance 1 month after transplantation. Conclusion: It can be concluded that the prevascularized PET mesh bag enabled transplanted BAP to survive and maintain function, thus indicating a potential site for BAP transplantation.