The coagulation and the stability of dilute colloids at high Peclet number were studied in consideration of the universal nonsingular van der Waals interactions recently developed by J, X, Lu and W, H. Marlow (1995, Phys, Rev. Lett. 74, 1724), The capture efficiency of gravitational coagulation of uncharged colloids was found to be diminished due to the effect of finite molecular size (EFMS), The gravitational coagulation stability diagram of charged colloids was also found to be shifted when the gravitational convection was much stronger than the Brownian diffusion.