. Preferential oxidation (PROX) of CO in the presence of H2 is an important reaction to maintain stable operation of polymer electrolyte fuel cells (PEFCs) since their anode catalyst can be poisoned by trace amount of CO. In this study, we examined PROX reactions mediated by Pt catalysts prepared using several mesoporous silica and aluminosilicate supports such as imogolite (IM), allophane (AP), silica aerogel (SAG), and an amorphous hydroxyl aluminosilicate developed in our research group (HAS). The selectivity of CO oxidation gradually decreased from 80 to 60 % with increasing temperature from 323 to 473 K for Pt/HAS catalyst whereas it increased with temperature from 10 to 40 % for Pt/IM, Pt/AP, Pt/SAG catalysts. These results indicate that Pt supported on HAS may be effective for low-temperature PROX reactions.