A lower mantle S-wave triplication is detected using short- and long-period SH seismograms in the distance range 70¿ to 95¿. Modeling of the observations with synthetic seismograms indicates that the triplication is produced by a 2.75¿0.25% shear velocity increase about 280 km above the core-mantle boundary. The SH data from intermediate and deep focus events for three distinct source region-receiver array combinations show generally consistent travel time and relative amplitude behavior of the triplication. There are small, systematic travel time shifts between the source regions which suggest regional variations in the depth of the discontinuity of up to 40 km.