This study describes the effects of some fiber types and geometrical characteristics on the dynamic compressive behavior of fiber assemblies. 15-gram specimens of fiber masses were compressed dynamically by means of a piston-cylinder device connected to a scotch yoke mechanism. Compression was carried out under LATIN SQUARE design with 5 replications and the identical runs were repeated at 6 different frequencies setting : 0.1, 0.5, 1.25, 2.5, 5 and 10Hz. Modelling fiber mass as a simple spring-mass-damper system, the stiffness coefficient k and viscosity coefficient c of the model were estimated from the obtained experimental values of amplitude ratios and phase angles. The effects of physical and dimensional properties of fibers on dynamic compressional properties were found as follows. 1. The effects of the fiber types on the values k and c is statistically significant at 1% level. And these values are larger for the acryl fiber, followed by polyester and nylon in this order. 2. The effect of the fiber fineness is statistically significant at 1% level. It was shown that the greater fiber fineness, the larger k and c values is. 3. The effect of crimp is statistically significant at 5% level.