First-principles total energy calculations were carried out in order to determine the local atomic geometry of the (110) surfaces for the isoelectronic series GaP, ZnS, and CuCl. Despite the large change in ionicity across the series (Phillips ionicities: fGaP=0.37, fZnS=0.62, and fCuCl=0.75), it was found that all three surfaces exhibit an activationless, bond-rotation relaxation with a rotation angle of ∼25° or greater. While this result is well known in the case of III–V (110) surfaces, it is in contradiction to a previous calculation which predicted that the bond-rotation angle would decrease with increasing ionicity, going to zero for CuCl. However, our results are in qualitative agreement with a recent dynamical low-energy electron diffraction analysis of the CuCl (110) surface. Despite the presence of a large-angle bond rotation for all three surfaces, the local atomic geometries depend on ionicity as follows: both the total energy gain for a given bond-rotation angle and the deviation of the surface anion from its ideal, bulk-terminated position decrease with increasing ionicity. In addition, the contraction of the top-layer anion–cation bond, relative to the bulk bond length, increases with increasing ionicity.