Abstract: Experimental studies of emulsion and suspensoon polymerization of styrene at 50~C are reported.Amathematical model for a batch emulsion polymerization in a unbaffled reactor with stirrer is proposed.This model allows for not only the effect of adsorption of the emulsifier onto the monomer droplets butalso the gel-effect.Data from the suspension polymerization tests are used to determine the relationshipbetween K_t and X_p Conclusion of these data in the model provided a good prediction of the number andsize of the latex particles and the conversion rate over most of the conversion range.