The goal of this paper was to experimentally investigate sedimentation of concentrated suspensions of monosized particles at low Reynolds number. Experiments were carried out with polymethylmethacrylate (PMMA) spheres of three different radii suspended in a fluid of matched refraction index. Laser Induced Fluorescence technique was used to determine the spatio-temporal evolution of particle concentration and displacement of sedimentation fronts. It was mainly possible to recognize the existence of specific modes that govern the sedimentation process when particle radius is changed. As a consequence, the maximum packing concentration of the sediment was found to be a decreasing function of particle radius and observed results were found to be well correlated with the corresponding Richardson and Zaki flux function. (C) 2014 Elsevier B.V. All rights reserved.