The reactivity of three perovskites containing cobalt in three different oxidation states, Co(II), Co(III) and Co (IV) has been studied under two types of gas flow composition : i) binary mixtures containing either CO + 02, CO + NO or C3H8 + 02 . ii) a complete gas mixture with CO + C3H8 + NO + 02 . In both cases nitrogen was the balance gas. The reactivity order is found always to be the same, whatever the reaction : Co304 > LaCoO3/Co304 ~ LaCoO3 > BaCoO2.x > Ba2CoWO6 , and is correlated to the reducibility of the samples followed by TPR. The first four catalysts exhibit the same reactivity for the CO + 02 reaction as classical Pt-A1203 and Pt-CeO2/A1203 catalysts, their light-off temperatures being between 430 and 500 K. These perovskites give reproducible results after the surface has been changed by the reactant gases, this phenomenon has been observed by the presence of a hysteresis, for Co304, under the CO + 02 gas mixture.