A review of recent progress in the understanding of structural and electronic properties of the low-index surfaces of group IV and III–V semiconductors is given and the “driving forces” for surface reconstruction are analyzed. The main conclusions from this study are that for group IV materials the reconstructions are always characterized by an increase in the bonding order at the surface. In contrast, for group III–V compounds the reconstructions are driven by substantial rehybridizations of dangling-bond orbitals and, simultaneously, by a tendency to lower the polarity of the surface. In some cases, such as the Ga-terminated (111) and As-terminated (100) surfaces of GaAs, the latter effect leads to an increased dangling-bond density at the reconstructed surface as compared to that on the ideal and unreconstructed surface.