Dynamic analysis of vertical seat suspensions of off-road vehicles is performed via computer simulation models in order to establish their ride performance. The PC-based computer simulation program is capable of analyzing various commercially available seat suspensions under different input excitations. The software is developed using the Visual Basic interface on Microsoft Windows platform and is entirely menu driven. The software is organized in a systematic fashion with the pre-processor, analysis and post-processing modules and has the option to choose any module from the initial selection screen. A database of various seat-suspension characteristics, along with other off-road vehicle input parameters is available in the pre-processor module. Analysis of the dynamic system is performed using a generalized two-degree of freedom model characterizing the vertical seat and suspension motion. The model incorporates the system nonlinearities due to shock absorber damping, coulomb friction and bump stops. The nonlinearities in the model are linearized using a local equivalent linearization technique based on energy similarity in order to compute the ride performance of the seat-suspension system. The base excitations from the cab floor on the seat-suspension system include both deterministic (sinusoidal and shock) and random input conditions. The post-processing module graphically presents the vibration attenuation characteristics of the seat-suspension in terms of the following performance criteria: (a) acceleration transmissibility and (b) Power Spectral Density (PSD) of acceleration response for the random input.