Pressure developed inside wool assemblies under constant-volume, cyclic, compressive loading has been investigated. Measured pressure value decreases with an increase in number of repeat cycles whilst it registers a higher value as the off-load interval (the time interval between two consecutive loading intervals) is increased. The regression curve is in excellent agreement with a decreasing exponential curve of the form Y=C+A exp (BX). Pressuer is affected strongly by the number of cyclic repeats and only slightly affected by the cyclic time interval when it is short whereas it is significantly affected by the cyclic time interval when it is longer. Volume deformation under constant compressive load increases with time, and this is expressible as decreasing exponential curve represented by this Y=C+A exp(Bt). By employing a three-parameter solid rheological model for the random fibre assembly at the constant load compression, two elastic moduli and a coefficient of viscosity were found to vary linearly with the density of fibre assembly at the first compression.