Emulsion polymerization of styrene/butadiene is simulated using the Monte Carlo (MC) method. To run the simulation some assumptions were made, some important examples of which include: Interval I is finished when all micelles have disappeared, the rate of monomer addition depends only on the nature of the terminal group. During the polymerization period no variation is considered for the reaction constants. A bimodal molecular weight distribution was obtained, which is evidence of tri-functional branching and tetra-functional crosslinking. The results show an increase in the degree of conversion, which leads to a shift in the molecular weight distribution toward higher values. An increase in the emulsifier concentration increases the surface area under the second peak in the molecular weight distribution. The MC simulation as a statistical approach, gave results that are in agreement with the Smith-Ewart theory for insoluble monomers in continuous media.