A large steric effect on XeBr* formation was observed in the reaction of oriented CF3Br with Xe(P-3). The reaction cross-section was found to be largest for the Br-end collisons and smallest for the CS3-end collisions, even though the electron transfer takes place at relatively large internuclear distances in the entrance channel. The large orientational dependence may be attributed to the fraction of the collisions that have small impact parameters which can lead to the formation of XeBr*. The majority of the collisions, having larger impact parameters, are supposed to lead to electron back-transfer in the exit channel and are relatively insensitive to the reactant orientation.