Abstract: A method for chlorinating the pendant methyl groups of poly(p-methylstyrene) with aqueous sodium hypochlorite (e.g., laundry or swimming pool bleach) and a phase transfer catalyst (e.g., benzyltriethylammonium chloride) to provide chloromethyl-substituted polystyrenes. Conversions of up to 20 percent of methyl to chloromethyl groups were achieved with no detectable formation of dichloromethyl groups. Conversions of up to 61 percent of methyl to chloromethyl groups occur with less than 4.4 percent concomitant formation of dichloromethyl groups. The method has been applied to soluble, 1 percent cross-linked, and macroporous 20 percent cross-linked polymers.