The effect of various monomer addition policies on the composition of a copolymer synthesized by semicontinuous emulsion copolymerization, using monomes with widely different ractivity ratios, was studied by mathematical simulation. Three policies were considered. In the first, both monomers are added under starved conditions. In the second, the reactor is initially chanrged with all of the less reactive monomer plus the amount of the mono reactive monomer needed to initially form a copolymer with the desired composition. Subsequent addition of the remaining monomer is made at a flow rate that ensures the formation of a copolymer of of constant composition. In the third, the initial charge is the same as in the previous case with subsequent addition of the remaining monomer at a constant fed rate. The copolymer composition obtained under starved conditions was almost constant in the cases where low feed rates were used. however, this led to long process times. For the second policy, a mathematical model ws developed to calculated the necessary addition rate of the more reactive monomer, that ensured the production of a copolymer of constant composition. It was found that the resulting process time was one third of that corresponding to the starved process. When variations in a copolymer composition were allowed, the third addition polycy might prove to be a good alternative to the second addition polyce because of iots shorter process time and teh advantage of working with teh constant feed rate.