A simple two-band model was used to investigate the influence of the multiconnec-tivity of the Fermi surface on the properties of superconductors. It was shown that the effect is analogous to that of anisotropy. The effect of impurity scattering was considered by the Green's function method of Абрикосов and Горъков. There is a unique energy gap for both bands in the presence of impurities. The new gap parameter is larger than the smaller one of the two gaps in the pure case. The critical temperature Tc, critical magnetic field Hc, and its temperature coefficient x near T=0°K are lowered with doping, while the jump in specific heat at the transition point is raised. The combined measurement of the relative changes of these quantities should provide a direct verification of the theoretical calculations. The properties of heavily doped two-band superconductors are identical with those in the single band case. Furthermore, the results obtained were used to discuss the tunnelling experiment on Pb films and the anomaly of critical temperature in the alloy systems of In-Sn and In-Pb.