An interpolation scheme for hcp transition metals is developed as an extension of Mueller's method. The band structures of fcc and hcp Co are calculated by KKR with a suitable potential, and the parameters in the interpolation scheme are determined so as to give the best fit. It is found that Mueller's scheme is well applicable to hcp Co. The density-of-states of Co is calculated and the topology of the Fermi surface of ferromagnetic Co is described. From the knowledge of the eigenvectors, the g -factor, the orbital magnetic moment and the coefficient of the magnetic anisotropy are calculated.