Annually, suspension polymerization produces kilotons of material with properties given by process conditions. The prediction of material properties requires a relevant description of processes on various scales from the molecular level to reactor design. The polymerization occurring on the molecular scale was described by a kinetic scheme of homopolymerization. The molecular level was connected to the meso-scale by the viscosity evolution inside a single monomer/polymer drop. The viscosity model follows the change in the reaction mixture composition and its predictions were validated by the rheology measurements. During the suspension polymerization, the viscosity evolution affects the dispersion breakage and coalescence on the meso-scale, which is closely connected to the flow conditions given by the reactor design and operation conditions. This complex problem was described by a coupled CFD-PBE model. The presented study proposes a modeling approach to control the suspension polymerization by stirring speed to obtain the desired drop size. (c) 2016 American Institute of Chemical Engineers AIChE J, 62: 4229-4239, 2016