A circulation model was created in 6 nonaneurysmal human cadavers to evaluate the deliverability, deployment, and acute performance of a modular branched endograft system for treatment of aortic aneurysms containing essential branch vessels. Two fenestrations were created in an appropriately sized aortic main endograft. Under fluoroscopic guidance, the main endograft was advanced to the target site and the fenestrations were aligned with the ostia of the renal arteries. Branch grafts were placed through the fenestrations into the renal arteries. The outcome was evaluated by post implant angiography and autopsy. Eleven branch grafts were deployed at the target site. All targeted renal arteries showed good patency. At autopsy, all main endografts were adequately deployed, and 10 of 11 branch grafts were locked in place. In this model, deliverability and deployment of the modular branch graft system is feasible in a reliable, predictable, and timely fashion.