Platinum and rhodium supported on alumina and titania were synthesized by the sol-gel method. Characterization and catalytic activity for the reduction of nitric oxide by carbon monoxide was performed. In sol-gel ＇sintered/reduced＇ catalysts＇ a redispersion of the metal phase and higher resistance to sintering was observed. On the other hand, in the impregnated ＇sintered/reduced catalysts＇, an important sintering effect was observed. The sol-gel ＇reduced catalysts＇ and ＇sintered/reduced catalysts＇ showed higher activity than that of impregnated reference catalysts, mainly when the titania is the support. Moreover, sol-gel preparations are more selective to N-2, whereas impregnated reference catalysts are selective to N2O. The increase in dispersion and high resistance to sintering on sol-gel ＇sintered/reduced catalysts＇ was interpreted as a surface migration effect of the metal particles buried in alumina and titania gels.