The linear combination of atomic orbitals (LCAO) method implemented in the CRYSTAL program for the study of periodic systems has been used to obtain wave functions, charge and spin densities of the most stable antiferromagnetic orderings of the MnS B-1 and B-3 polymorphs. The calculations have been led to the density functional (DF) level of theory by solving the Kohn-Sham equations self-consistently. One local and one gradient exchange-correlation (XC) potentials have been studied for comparison with the Hartree Fock (HF) results. Electron charge and spin densities have been calculated and the neutron diffraction of the two polymorphic forms of MnS deduced. Comparison of our results with the experimental data is discussed.