Abstract: The existence and properties of localized electronic states are described in binary (two layers per period) semiconductor superlattices. Special attention is paid to surface effects, due to the superlattice potential termination by a clad layer, and the resulting Tamm-like surface states localized at the superlattice/clad-layer interface. Kronig-Penney-like approach within the framework of effective-mass and envelope-function approximation is used for bulk- and surface-electronic-structure calculations of terminated binary superlattices. The description of short-period Al_x Ga_{1-x} As-based superlattices, taking into account the elastic Gamma-X intervalley transfer by introducing an additional $\delta$-functional scattering potential at each well/barrier heterointerface is presented. Modification of the energy spectrum and the localization properties of SL surface states with respect to previous single-band treatments is clearly indicated, and identified as a result of the Gamma-X interband coupling.