Photopolymerization of styrene inititated by tetraphenyl cyclopentadiene triphenyl bismuthonium ylide in dioxane was carried out in the presence of visible light (440 nm) at 30 +/- 0.2 degrees C for 55 h. The polymerization was inhibited by the presence of hydroquinone which is an evidence of the fact that polymerization; takes place by radical mechanism. The system follows ideal radical kinetics [R-p proportional to [I](0.5) [M]). The values of average degree of polymerization ((P) over bar(n)) decreases with the ylide. The mechanism of the reaction was elucidated by GPC and ESR techniques.