Polymerizations of styrene were carried out with half-sandwich complexes supported on silica, CpTiX3/MAO/SiO2 (X = Cl, F). The optimum values for the polymerization time, the amount of cocatalyst and the Al-support/Ti ratio were found for the trichlorinated system. The highest activity obtained was 3,100 g sPS/(mol Ti x h x mol/L styrene), The trihalogenated complexes were compared to one another with respect to their polymerization rate. CpTiCl3/MAO/SiO2 and CpTiF3/MAO/SiO2 behave in a similar manner, suggesting that the active species of both half-sandwich complexes on the support are the same. Furthermore, aging experiments were carried out with CpTiCl3/MAO/SiO2 and, surprisingly, deactivation was observed, as opposed to supported zirconocenes which gain stability against deactivation reactions when anchored to a carrier.