The electronic structure of the A15 compounds A 3 B A=Nb; B=Al,Ga,Ge,Sn and In is studied by means of fully relativistic full-potential linearized augmented-plane wave (FP-LAPW) calculations within the formalism of the density functional theory. Band structures and densities of states are determined for all the studied compounds. From the calculations are obtained the theoretical lattice constants, the Fermi energy E F , the density of states at the Fermi level N(E F ) which is used to estimate the electronic specific heat coefficient γ and the electron-phonon coupling parameter λ for the Nb 3 In compound. Generally, a good agreement between results of the calculations and experiments is found.