  Globular clusters (GCs) are spheroidal concentrations typically containing of
the order of 10^5 to 10^6, predominantly old, stars. Historically, they have
been considered as the closest counterparts of the idealized concept of "simple
stellar populations." However, some recent observations suggest than, at least
in some GCs, some stars are present that have been formed with material
processed by a previous generation of stars. In this sense, it has also been
suggested that such material might be enriched in helium, and that blue
horizontal branch stars in some GCs should accordingly be the natural progeny
of such helium-enhanced stars. In this contribution we show that, at least in
the case of M3 (NGC 5272), the suggested level of helium enrichment is not
supported by the available, high-precision observations.
