A test facility has been developed utilizing engine dynamometers to age catalyst. The engine operating parameters and thus the input to the catalyst were set to duplicate the environment of the catalyst during vehicle test on the Federal Appendix D Durability Schedule. Results from the experimental car durability test have shown that the primary cause of catalyst performance loss on this schedule has been due to contamination build-up on the catalyst surface. Catalyst aged on the engine dynamometer facility has shown very good performance loss correlation to similar catalyst aged in the vehicle test. This correlation has allowed the use of this engine dynamometer facility to investigate various catalyst parameter effects on the durability performance of the catalyst.