The sedimentation of solid particles of simple form and complex form has been studied. The applied data in the case of isometric particles have been compared to those of spherical particles of same volume. This comparison allows highlighting an equivalent sedimentation diameter concept. Dimensionless factor depending on the extended equivalent diameter, the geometric aspect of the particle and the flow have been defined. The use of this factor allows finding an interrelationship with another dimensionless factor which is the Archimedes number. This last depends on the physical parameter of the particle and the carrying fluid. The numerical treatment of this interrelationship permitted to deduct an empirical model for the settling velocity of particles. This model is applied with success to the data of the considered measures and well compared to the results obtained by other models. (c) 2007 Elsevier B.V. All rights reserved.