The performance of a new monolith-type automobile exhaust catalyst is described. The catalyst under development employs a high-melting ceramic substrate (with about 200°C margin over cordierite). The washcoat's performance was found to be sufficient to permit a reduction of the catalyst's volume by about 30% while still showing competitive performance versus a full-size commercial catalyst. Engine dynamometer and vehicle emission test data are discussed for illustration.The new ceramic has a higher density than cordierite; the paper discusses the effects of catalyst density on emission performance in the heat-up and cool-down portions of emission cycles. The results show no density penalty in FTP tests with the new ceramic.