We study interfaces between highly ionic crystals with different crystal structure by first-principles total-energy calculations in the repeated-slab approximation and compare the results with experimental data extracted from high-resolution transmission electron micrographs. The nonpolar (1 1 0) interface between PbTe (rocksalt) and Me (zinc-blende) crystals gives rise to a lateral spatial offset between the two crystal halves. At the polar (1 0 0) interfaces a strong variation of the interface extent with respect to the cation or anion termination is observed. Furthermore, we calculate band offsets and projected interface band-structures for PbTe/CdTe interfaces. The results are discussed versus the interface orientation. (C) 2007 Elsevier B.V. All rights reserved.