Background.Pancreatic islets are avascular immediately after transplantation and depend on revascularization. Recently, the authors found decreased vascular density in mouse islets 1 month after implantation into nondiabetic recipients. This study investigated possible differences in revascularization between islets implanted into nondiabetic and diabetic recipients, and also evaluated changes in vascular density up to 6 months posttransplantation.Methods.Islets were syngenically transplanted beneath the renal capsule of normoglycemic or alloxan-diabetic C57BL/6 mice. One to 6 months later, the animals were killed and the grafts removed. Histologic slides were prepared and stained withBandeiraea simplicifolia.Results.The vascular density in all transplanted islets was decreased compared with native islets. There were no differences in the islet graft vascular density between nondiabetic and diabetic animals. No improvement over time occurred.Conclusions.The vascular density is decreased in islets implanted to cure diabetic recipients. No improvement occurs in transplanted islets after 1 month posttransplantation.