The comfort assessments of automotive seats are attempted through development of seat-occupant models in order to minimize the participation of human subjects in such studies. A nonlinear model of a polyurethane foam (PUF) cushion and its support mechanism is developed through measurement of static and dynamic properties as functions of the seated load, and excitation frequencies and amplitudes. Nonlinear analytical models of the seat-occupant system are developed by integrating three different occupant models of different complexities with the cushion model. The analytical response characteristics of these models are derived under sinusoidal and random excitations considered representative of the automotive vibration environment. The vibration transmission properties of the seat are measured in the laboratory under harmonic and random excitations using 6 human subjects. The response characteristics of the models are compared with the mean measured response characteristics to examine the validity of occupant models for automotive applications. From the comparison, it is concluded that the reported occupant models yield poor estimates of vibration transmission performance of automotive seats.