This paper reports the free radical dispersion copolymerisation of methyl and ethyl methacrylate in supercritical carbon dioxide. The polymerisation uses a poly(dimethyl siloxane) monomethacrylate macromonomer as the stabiliser. A range of different reaction times was investigated in order to probe the amount of each monomer incorporated in the copolymer. Analysis by H-1 NMR spectroscopy reveals that the monomers behave as in conventional solvents to form a random copolymer. The effect of varying the initiator concentration (initiator 2,2'-azobisisobutyronitrile, AIBN) on the composition and molecular weights of the resultant copolymers has also has been studied.