Yields of massive stars and their role in galactic chemical evolution studies

We review the yields of intermediate mass elements (from C to Zn) from mass ive stars and their associated uncertainties, in the light of recent theore tical results. We consider the role of those yields for our understanding o f the chemical evolution of the solar neighborhood and of the halo of our G alaxy. Current yields reproduce in a satisfactory way the solar system comp osition, but several problems remain concerning abundance ratios in halo st ars. (C) 2000 Elsevier Science B.V. All rights reserved.