We present full-potential self-consistent linearized augmented plane wave (LAPW) calculations for the electronic structure and total energy of MgO and CaO, within the local density approximation. Calculated equilibrium properties are in good agreement with experiment. We also consider the transition from the low-pressure sodium chloride (B1) structure to the high-pressure cesium chloride (B2) structure for MgO and CaO and the transition to the NiAs (B8) structures for MgO. In calcium oxide we find that transition from B1 to B2 transition occurs at 54 GPa, in agreement with the experiment. In magnesium oxide a pseudopotential calculation. We find no transition to the B8 structure at any pressure. The calculated charge densities of MgO and Cao are close to the charge densities calculated from the overlap of spherical ions used in the potential induced breathing (PIB) model at zero pressure. More significant deviations from overlapping ions are found at extreme pressures. Near equilibrium, the error in the PIB model (compared to the LAPW calculation) is of the same order as the error in the LAPW calculation (compared to the experiment). ¿ American Geophysical Union 1988