We have constructed a parametric many-body potential that gives accurate predictions of high pressure properties of alkali-earth oxides. The model incorporates ionic deformational energy and a repulsive potential that are sensitive to the crystal environment. This feature is accomplished by an explicit dependence of the size of oxygen on the crystal potential. The parameters of the model are constrained by equation of state and zero pressure elastic constants of the B1 (NaCl) phases. The model predicts accurate B1-B2 transition pressures and densities of the B2 (CsCl) phases. Elastic moduli are reproduced exactly, and accurate pressure derivatives are predicted. ¿ American Geophysical Union 1988