Organosilane reagents are introduced into organotitanium-mediated styrene polymerizations to produce atactic polystyrene with high activities (up to 10(6) g polymer/(mol Ti.h)) and narrow polydispersities. Previously recognized CGCTiMe(2) systems having marginal styrene homopolymerization activity are shown to be up to 3 orders of magnitude more active for styrene homopolymerization upon addition of organosilane.