The authors have studied the electronic energy structure of pseudomorphic Gem/Sin superlattices by using the empirical tight-binding method. Effects of the band offset, sublattice periodicity and the lateral lattice constant on the transition energies have been investigated. They found that GemSin superlattices grown on Ge (001) can have a direct band gap, if m+n=10 and m=6. However, optical matrix elements for in-plane and perpendicular polarized light are negligible for the transition from the highest valence band to the lowest conduction band state at the centre of the superlattice Brillouin zone.