Pre-existing flaws in materials are the potential source for brittle fracture in compression just as in tension. As in tension, both the stress and energy criteria should be taken into account for brittle fracture in compression. In the model presented, flaws are represented by three-dimensional ellipsoids, thus removing certain limitations of previous two-dimensional models. The formulation of the changes in the potential energy of the applied load and the strain energy of the infinite medium due to the introduction of an ellipsoidal void is presented and the implementation of the numerical calculation of the stress concentration and the energy release rate is developed. The required three-dimensional theory for a better understanding of brittle fracture in compression is provided.