This report on Microstructural and Physical Basis for Superplastic Cavitation in Aluminum Alloys embodies work carried out jointly between PhD student Donghyun Bae and Professor Amit Ghosh and in direct collaboration with General Motors R&D Center, Pacific Northwest National Laboratory and Air Force Research Laboratory. Considerable new information on the initiation of nanoscopic damage in A1 alloys, and the growth of voids through the microscopic and mesoscopic scales has been developed in this work. New information on the role of stress-state on void growth has been obtained. It has been shown that underpredictions of previous models of void growth are related to the lack of recognition of local stress-concentration effects surrounding the voids, persisting even at elevated temperatures.