Abstract
We analyse in detail the standard primordial nucleosynthesis scenario. In particular, we discuss the key theoretical issues which are involved in a detailed prediction of light nuclide abundances, such as the weak reaction rates, neutrino decoupling and nuclear rate modelling. We also perform a new analysis of available data on the main nuclear processes entering the nucleosynthesis reaction network, with particular stress on their uncertainties as well as on their role in determining the corresponding uncertainties on light nuclide theoretical estimates. The current status of theoretical versus experimental results for 2H, 3He, 4He and 7Li is then discussed using the determination of the baryon density as obtained from cosmic microwave background anisotropies.