Abstract
The importance of a good determination of the primordial He abundance (Y[p]) has been extensively discussed in the literature. The method generally used to obtain Y[p] was proposed by Peimbert & Torres-Peimbert (1974) and makes use of a correlation between the He mass fraction (Y) and metallicity, extrapolated to zero metallicity. Since the statistical uncertainties in the determination of Y[p] are very small ( ~ 1%), it is essential to discuss possible systematic errors in the determination of Y and consequently of Y[p].
