Attention is drawn to the lack of a successful theoretical model for calculation of the effect of solids concentration on the settling velocity of particles from suspension. The principal challenge to formulation of a model is solution of the equations of fluid motion through an ensemble of solid particles which are randomly distributed to space. A new theoretical model which addresses this difficulty is presented. It is based on permeation of the fluid through a structure composed of cells each of which consists of a single spherical particle and an associated body of fluid. The quantity of fluid in each cell is a random variable. Using this model, the settling velocity of a suspension at substantial volume fraction can be calculated without resort to empirically determined factors. Good agreement with experimental settling velocities is obtained.