[en] The new proposed Appendix B to 10CFR100 requires that both probabilistic and deterministic evaluations be made. The details of how to perform these evaluations are outlined in the proposed draft Regulatory Guide DG-1015. In DG-1015, one element of the probabilistic evaluation recommends determining the controlling earthquake from the probabilistic seismic hazard analysis (CE-PA). In this paper, the concept of the CEPA is discussed along with the approach that is suggested to determine the CE-PA. This paper reviews the basis for the various key choices that must be made. We also apply the approach to eight sites using the LLNL seismic hazard methodology developed for NRC