The activity behavior of carbon monoxide and propene oxidation on Cu-Cr catalysts was investigated by varying both the catalyst composition and the heat-treatment conditions. gamma-Alumina supported CuO, Cr2O3 and Cu-Cr oxide catalysts were employed. The Cu-Cr catalysts were treated by heating at 300-900 degrees C under oxidizing or reducing atmosphere. Calcined at 700-900 degrees C under oxidizing atmosphere, the formation of Cu2Cr2O4 spinel structure resulted in an enhanced activity not only for carbon monoxide oxidation but also for propene oxidation. On the other hand, treatment in a reducing atmosphere at 700-900 degrees C produced a sintered copper surface but induced a strong metal-support interaction that led to an enhancement in activity, but only for carbon monoxide oxidation. Additionally, the synergistic effect resulting from the ligand effect, as Cr2O3 species is closely associated with CuO species, occurs for carbon monoxide oxidation, The activity of propene oxidation on the CuO catalyst reaches a maximum at a copper content of about 10 wt.-% and that on the Cr2O3 catalyst reaches a maximum at a chromium content of about 25 wt.-%.