Research on aggregation and breakage processes of solid particles suspended in a liquid has been carried Out. The experiments were performed in two laboratory mixers equipped with a turbine, propeller and vibrating mixers. In description of the evolution of the aggregate population, a mathematical model based on population balance equations was employed. The population balance equations were solved using special procedure in Turbo Pascal enabling one to calculate optimum values of kinetic parameters of both processes. The model and numerical procedure proposed can be used in analysis of aggregation and breakage.