Diffusion bonding (DB) of superplastic 7075 Al alloy has been investigated for various temperatures, pressures and times, using a Gleeble 1500 test machine. After the removal of surface oxide, an organic solution was used to protect the surfaces prior to bonding. The strengths achieved after bonding were dependent on interface grain boundary migration and on grain growth during the bonding process. Under optimum conditions, bonds having parent metal shear strength and microstructure were obtained. The optimum temperatures for diffusion bonding, 510–520°C, corresponded with those at which the material exhibited optimum superplastic behavior. The characteristics and mechanisms of bonding are discussed.