The effect of soil-structure interaction on the structural response to earthquake motion is analyzed. The structure is modeled by a one degree-of-freedom system resting on an elastic half space. The soil is then approximated by simple mass-spring dashpot systems using the solutions obtained by G. N. Bycroft for the soil compliances. The resulting dynamic model is expressed by nondimensional parameters. The input motion is first assumed a white noise process, and the maximum response is replaced by the rms response.