In this study, we employ a multistate generalized Mulliken-Hush approach for calculating electronic couplings V-da for charge transfer (CT) in DNA pi-stacks consisting of three, four, and five base pairs. In these systems the guanine donor and acceptor sites are separated by several (AT) pairs. The Hartree-Fock calculations of the stacks are carried out with the standard 6-31G* basis sets. All possible superexchange pathways are accounted for. We examine electronic couplings estimated using the two-state and multistate models. Although for some systems the two-state scheme provides reasonable estimates of V-da, in general this simple model fails to reproduce the electronic couplings calculated with the multistate approach. The two-state treatment of pi-stacks with a tunneling gap less than 0.3 eV, for instance, GAAG and GAAAG, may lead to invalid estimates of V-da. We consider the dependence of V-da on the length and composition of the bridge. The calculations show that V-da is less sensitive to the arrangement of nucleobases in the bridge, as can be predicted on the basis of electronic couplings between adjacent base pairs.