The rate of gravity-induced coagulation of a dilute polydisperse suspension of small particles is considered by incorporating gravitational and interparticle forces (both attractive and repulsive), as well as hydrodynamic interactions, When electrostatic repulsion is significant, particles can coagulate into either a primary or secondary minimum (as described by DLVO theory), or remain dispersed, Spherical sols can be unstable at low and high gravitational forces, but stable against gravity-induced coagulation at intermediate and higher values when Brownian motion can be neglected.