Anabinitiocalculation of the electronic structure in amorphous silicon based on Henderson’s 61‐atom quasiperiodic lattice model has been made by using the method of linear combinations of atomic orbitals. The use of the Gaussian technique makes it quite easy to evaluate all the necessary multicenter integrals and the lattice summation is carried out to convergence. The calculated density of states is in good agreement with experiments. The band structures of silicon in two polycrystalline forms have been calculated also by the same method. Comparison of their density of states with that of amorphous silicon is discussed with special reference to distortion from the perfect tetrahedral coordination.