  The status of the art for evolutionary models of low mass, population II
stars is revisited, stressing the need for the models to be preliminarily
tested with suitable observational data. The uncertainties still affecting the
theory are discussed in the aim of guiding the users in a reasoned choice of
the models. The powerful coupling of evolutionary with pulsational theories is
shortly recalled. A short conclusion and a mention of the problem of tilted HB
close the paper.
