The tunneling currents method developed previously by this group for the description of electron tunneling in proteins and other complex molecular structures is implemented at the semiempirical ZINDO level. This implementation bridges the gap between fully ab initio and simple one electron methods, such as the extended Huckel method, which has been previously employed in tunneling studies, and allows for accurate calculations to be performed on realistic large protein systems with only a moderate effort. One additional advantage of this method is that it employs the STO basis functions, which decay more slowly than do GTO functions, so that the weak tunneling interactions of noncovalently bonded atoms of the protein can be accounted for with a minimum basis set. Numerical results are demonstrated on the polypeptide chain (His)(2)(Met)Cu1+-(Cys)-(Gly(5))-(His)Ru-3 (+)(bpy(2))Im, which models the Ru-modified azurin charge transfer system studied by Gray and co-workers.