  Recent observations of 3He/H in different environments tend to prove that 3He
is not produced in low mass stars, contrary to the standard predictions of
stellar evolution theory. We show how a simple consistent mechanism, namely
rotation-induced mixing, can lead to the destruction of 3He in low mass stars
and simultaneously account for the low 12C/13C ratios and low lithium
abundances observed in giant stars of different populations. This process
should both naturally account for the recent measurements of 3He/H in galactic
HII regions and allow for high values of 3He observed in some planetary
nebulae.
