Evolutionary models of zero metallicity stars

We present new evolutionary models for zero-metallicity stars, covering a large range of initial masses (from 0.8 to 100 M_ 99). Models are computed with overshooting from stellar cores and convective envelopes, and assuming mass-loss from the most massive stars. We discuss the main evolutionary features of these stars, and provide estimates of the amount of newly-synthesized elements dredged-up to the stellar surface, and possibly lost by stellar winds from the most massive stars. Full details of these models will be given in Marigo et al. (2000, in preparation)