The mathematical models of acrylonitrile-butadiene-styrene (ABS) latex coagulation processes that show the effect of major operation variables on the particle-size distribution of recovered resins were derived-to provide a guideline for process improvement to reduce the content of fine particles in the product. Kinetic equations for the coagulation and breakup of particles taking place in a turbulent flow field were incorporated into the population balance models for batch and continuous processes. A dimensional analysis for the process models leads to two dimensionless groups, eta(c) and eta(b) that represent the relative intensity of the coagulation and breakup phenomena. The eta(c)/eta(b) ratio is designated as a design variable for controlling the particle-size distribution in the steady-state operation of the coagulation processes. This role is demonstrated by numerical simulation where increasing the ratio shifted the particle-size distribution toward large particles. The estimates of eta(c)/eta(b) obtained for a set of batch experiments also confirm that fine particles can be reduced by setting the operation variables to increase the ratio.