The shear-induced inertial migration of a rigid sphere has been studied experimentally using a homogeneous shear flow apparatus. The experimentally measured migration velocities have been compared with those predicted by the asymptotic formulas previously given by Saffman and McLaughlin. The analysis of a sphere translating in a shear field in the presence of a single wall has been extended to the case of a sphere translating in a fluid undergoing a uniform shear between two parallel walls.