Epicenters of large shallow earthquakes (M?6.9) of the past 55 yr and their aftershocks were recomputed for the western boundary of the Philippine Sea plate. These large shocks were not evenly distributed along the plate margin but clustered, particularly near Taiwan and near the islands of the central and southern phillppines. The concentration of large earthquakes near Taiwan is approximately confined to the area where continental lithosphere of the Asian plate appears to be colliding with remnants of the Luzon arc. Large shocks were infrequent near the central Ryukus and west of Luzon along a segment of the Manila Trench. In both of these locations, major bathymetric features near the trenches may be interacting with the subduction margin. Thus the variations in size and frequency of large events correspond spatially to changes in the tectonic conditions of plate convergence along the margin. The uneven distribution of large shocks therefore may represent a long-term pattern of occurrence. Segments of the plate boundary near the southwestern Ryuku are and near the Phillipine Trench are suggested here as areas of seismic potential in that these regions have a past record of large shocks and have tectonic similarities to other seismic zones where long intervals of quiescence culminated in large earthquakes. The techniques used previously to identify areas of seismic potential do not appear applicable, however, to much of this plate margin, particularly to those segments which consist of broad irregular zones of deformation. Recomputation of epicentral data prior to 1964 moves several large shocks closer to the trace of the Philippine Fault from both the east and the west. These relocated epicenters, combined with both recent data and historic descriptions, suggest that much of the fault may have been active during the past century.