Big Bang nucleosynthesis and the baryonic content of the universe

A review of the latest measurements of the primordial abundances of the light nuclei D, 3He, 4He and 7Li is given. We discuss in particular the primordial abundance Yp of 4He as measured in blue compact dwarf galaxies. We argue that the best measurements now give a ``high'' value of Yp along with a ``low'' value of D/H, and that the two independent measurements are consistent within the framework of standard Big Bang nucleosynthesis with a number of light neutrino species Nnu = 3.0+/-0.3 (2sigma).