A procedure for the calculation of chord length distributions (CLD) of populations of rigid and opaque particles of any size and shape distribution is given. It combines the capabilities of a virtual reality renderer to create 2D projections of particles and of an image analysis software which determine their chord lengths. The procedure has been validated on simple shapes (spheres, ellipsoids, parallelepipeds, cuboids, uniform polyhedra) that can be combined to simulate agglomerates or twinned crystals. The procedure has been used to discuss the experimental results obtained on gibbsite particles in different size ranges and to compare the mean chord length to the average particle size. (c) 2006 Elsevier Ltd. All rights reserved.