We test different Big Bang Nucleosynthesis scenarios using the recent results on the Cosmic Microwave Background Anisotropies provided by the BOOMERanG and MAXIMA-1 experiments versus the observed abundances of 4 He, D and 7 Li. The likelihood analysis, based on Bayesian approach, shows that, in the case of high deuterium abundance, YD = (2.0 ± 0.5)10 −4 , both standard and degenerate BBN are inconsistent with the CMBR measurement at more than 3σ. Assuming low deuterium abundance, YD = (3.4 ± 0.3)10 −5 , the standard BBN model is still inconsistent with present observations at 2σ level, while the degenerate BBN results to be compatible. Unless systematics effects will be found in nuclide abundances and/or in CMBR data analysis this result may be a signal in favour of new physics like a large chemical potential of the relic neutrino-antineutrino background.One of the main goals of modern cosmology is the knowledge of the energy density content of the universe. The four parameters Ω B , Ω CDM , Ω ν and Ω Λ , giving, respectively, the baryon, cold dark matter, neutrino and cosmological constant contributions to the total energy density, in unit of the critical density, and the Hubble constant, H 0 = 100h Km s −1 M pc −1 , enter as crucial parameters in several cosmological observables. A well known example is provided by the baryon density parameter which plays an essential role in determining the abundances of light nuclides produced in the early universe. An increasing interest has been also devoted to other issues, as structure formation and the anisotropy of the Cosmic Microwave Background Radiation (CMBR). As for our theoretical understanding of the Big Bang Nucleosynthesis (BBN), to test the theoretical models which describe these aspects of the hot Big Bang model, it is essential to have precise measurements of the several Ω i h 2 . Furthermore, combining different cosmological observables, and comparing the way they are able to constrain the Ω i h 2 , allows for a check of the consistency of our present understanding of the evolution of the universe. This can provide new hints on phenomena which took place at the macroscopic cosmological level, or rather related with the very microscopic structure of fundamental interactions.This letter represents a contribution in this direction. In particular, we do perform a combined analysis of the dependence on the energy fractions Ω B h 2 and Ω ν h 2 = N ν Ω 0 ν h 2 for massless neutrinos (N ν standing for the effective neutrino number and Ω 0 ν h 2 for the energy contribution of a single ν − ν specie) of CMBR anisotropies and BBN. This is aimed to test the standard and degenerate BBN scenario, using the recent results of the BOOMERanG [1] and MAXIMA-1 [2] CMBR experiments and the measurements of 4 He, D and 7 Li primordial abundances.The theoretical tools necessary to achieve this goal are nowadays rather robust and the accuracy in the predictions of the Big Bang model is remarkably improved. In fact, recently, a new generation of BBN codes have been developed [3][4]...