Bismuthoniumylide-initiated radical copolymerization of methylmethacrylate with styrene at 60 +/- 0.2 degreesC using dioxane as an inert solvent, follows ideal kinetics (R-p proportional to [ylide](0.5) [MMA](1.0) [sty](1.0)), and yields alternating copolymer as evident from NMR spectroscopy. The values of reactivity ratios r(1) and r(2), calculated from Finemann-Ross method are 0.48 and 0.45, respectively. The system follows ternary molecular complex mechanism. The radical mode of polymerization has keen confirmed by ESR spectroscopy and the effect of hydroquinone. The value of activation energy and k(p)(2)/k(t) are 65.0 KJ mol(-1) and 2.5 x 10(-5) mole(-1) s(-1), respectively.