  We follow the evolution of 3He in stars of mass 0.8 -- 10 M (solar units) for
Pop. I and II compositions from the main sequence until advanced stages on the
AGB. Under standard assumptions we confirm earlier results of more restricted
investigations that low-mass stars up to 5 M are net producers of 3He. We show
that the inclusion of additional mixing due to diffusion beneath the convective
envelope simultaneously leads to observed carbon isotope anomalies observed in
globular cluster Red Giants and to a strong reduction of 3He, such that stars
exhibiting such anomalies will have destroyed 3He contrary to the standard
picture.
