Homogeneous catalyst precursors of the forms RhCl(PPh(3))(3) and RhH(PPh(3))(4) are applied commercially for the selective hydrogenation of acrylonitrile-butadiene copolymers. This report details a study of their catalytic behavior at reaction conditions approaching those found in industrial settings. Detailed kinetic and selectivity data, collected according to a statistical design framework, have clearly defined the effect of varying process conditions. The kinetic results suggest the behavior observed under severe conditions is consistent with that reported for pressures and temperatures near ambient. Dilute solution viscosity data are used to demonstrate the uniform selectivity of both RhCl(PPh(3))(3) and RhH(PPh(3))(4) catalyzed hydrogenations. A probable reaction mechanism for the RhCl(PPh(3))(3) system has been derived using analysis of variance model discrimination procedures.