This paper describes the dynamic behavior of the six story seismically isolated building constructed on soil with inclined bedrock, based on strong motion records along with an evaluation of pile stress. The ground under the building has a two-layer structure composed of bedrock and deposit soil, where the bedrock depth is inclined toward the east-west direction. The foundation system is composite of a spread foundation and cast-in-place concrete piles with variable lengths according to the inclination of bedrock. The strong motion records are observed at the center and edges on the upper and lower floors of the seismic isolation layer.
 First, the seismic motions in deposit soil overlying the inclined bedrock are evaluated with a combination of SH and SV analyses using two-dimensional (2-D) FEM. Seismic response analyses are performed using a three-dimensional (3-D) full frame model consisting of the superstructure, seismic isolation devices and piles. The 3-D model is validated by comparison with strong motion records from the first floor and the basement. Then, the dynamic behavior of the seismic responses of the superstructure and pile stresses are evaluated and discussed. The conclusions of this study are summarized as follows:
 1. The displacement of the piles and surrounding soil increases as the depth of the bedrock increases. However, the displacement of the piles tends to be smaller in the longitudinal direction than the displacement of the soil, because the pile head was constrained by the mat slab.
 2. The bending moment and shear force at the spread foundation is larger than any other piles regardless of the direction of the inclination. The bending moment of the piles in the longitudinal direction is larger at the pile head due to the constraining effect of the mat slab, and in the middle section of the piles due to the kinematic effect of the soil seismic response.
 3. In the structural design scheme for pile stress evaluation, the 1-D model assumes a horizontally flat layer for each pile location. The bending moment and shear in the 1-D model were overestimated in comparison with those of the 2-D model.