The rheology of semidilute suspensions of rigid polystyrene ellipsoids at rotational Peclet numbers greater than 10(3) was studied for two different aspect ratios. The ellipsoid suspensions exhibit shear thinning behavior for both aspect ratios, similar to previous experiments on suspensions of rigid fibers. Possible mechanisms for the rate dependent rheology are discussed and evaluated through a comparison with the rheology of suspensions of spheres with the same material properties as the ellipsoids. For the largest Peclet number, the relative viscosity scales linearly with dimensionless number density and is independent of the aspect ratio. (C) 2008 The Society of Rheology.