The main scope of the present paper is to study the rigorous problem of coupled gravity-induced/Brownian flocculation for the strong Brownian/weak gravity case, by solving the coupled Langevin type equatio is on determining the Brownian particles' collision trajectories. When comparing with the previous results, our numerical calculated flocculat on rates are as good as those solutions obtained from using the singular perturbation expansion method to solve the steady state governing convective diffusion equation. Our solutions also confirm that the effect of Brownian diffusion can decrease the flocculation rates of colloidal particles under the condition of strong Brownian/weak gravity. (c) 2006 Elsevier Inc. All rights reserved.