Abstract: The effect of water soluble and monomer soluble inhibitors on the kinetics of emulsion polymerization of monomer following Case II kinetics (e. g. styrene) has been investigated. Experimental studies reveal that inhibitors can bave an appreciable effect on both polymer particle nucleation and growth. A mathematical model showing these effects has been developed and simulation studies have been made. The simulation results imply that the behaviour of monomer soluble inhibitors may be severe in industrial emulsion polymerization.