A 2.3 PCF commercially produced cellular polyethylene cushioning was vibrated under simulated in package conditions. Tests were performed on several as produced and on a laminated thickness. Vibration was imposed on samples under static loads from 0.20 to 2.0 psi. Transmissibility was recorded in the frequency range 2 to 250 Hz. It was observed that vibration behavior was strongly influenced by material preload state. Effects are discussed and illustrated by dynamic force vs deformation curves measured in package. One preload state is shown to induce configurational nonlinearity while another is found capable of suppressing a specific type of nonlinear reaction peculiar to compression-loaded cushioning. Pertinence of observations to utilization of cushioning in protective suspensions is considered. A technique for normalizing nonlinear cushion response data is developed. Results of comprehensive tests on polyethylene foam are reduced to this format. Data indicates the dynamic stiffness of the foam at transportation-induced vibration frequencies is increased significantly over values derived from low rate 1.0 in.min compression tests.