Results of the recently completed seismic evaluation at the Los Alamos National Laboratory site indicate a need to consider seismic loads greater than design basis for many structures systems and components (SSCs). DOE Order 5480.28 requires that existing SSCs be evaluated to determine their ability to withstand the effects of earthquakes when changes in the understanding of this hazard results in greater loads. In preparation for the implementation of DOE Order 5480.28 and to support the update of the facility Safety Analysis Report, a seismic margin assessment of SSCs necessary for a monitored passive safe shutdown of the Plutonium Processing Facility (PF-4) was performed. The seismic margin methodology is given in EPRI NP-6041-SL, ''A Methodology for Assessment of Nuclear Power Plant Seismic Margin (Revision 1)''. In this methodology, high confidence of low probability of failure (HCLPF) capacities for SSCs are estimated in a deterministic manner. For comparison to the performance goals given in DOE Order 5480.28, the results of the seismic margins assessment were used to estimate the annual probability of failure for the evaluated SSCs. In general, the results show that the capacity for the SSCs comprising PF-4 is high. This is to be expected for a newer facility as PF-4 was designed in the early 1970's. The methodology and results of this study are presented in this paper.