Observational evidence for rotationally induced mixing in massive stars is summarized. From these observations and the models required to explain them, we conclude that rotation will increase the primary metal yields of massive stars, enhance the production of H-burning secondary products (e.g. 14N and 26Al), and reduce the initial stellar mass limit for Type II supernova explosions. For the first time, these features are described quantitatively in the context of new evolutionary models for mass losing, rotating stars. These calculations include the effects of the centrifugal force on the structure as well as angular momentum transport and chemical element diffusion. The chemical yields of these models are presented and compared to those of other models evolved without rotation. Our models also indicate the presence of qualitatively new nucleosynthesis channels which may result in primary 14N production in the H-burning shell and primary neutron processing in the He-burning shell of rotating stars. Implications for the supernova explosion and neutron star remnant are briefly described.