  We report the results of a new accurate evaluation of light nuclei yields in
primordial nucleosynthesis. All radiative effects, finite nucleon mass, thermal
and plasma corrections are included in the proton to neutron conversion rates.
The relic densities of He4, D and Li7 have been numerically obtained via a new
updated version of the standard BBN code. In particular the theoretical
uncertainty on He4 is reduced to the order of 0.1%.
