The interaction of sintered low-loaded Re/ γ-Al 2O 3 catalysts with oxygen has been studied over a wide temperature range, 20–800 °C. The structure of the catalyst was characterized using different techniques: H 2 chemisorption, O 2 uptake, BET, TEM, and also by Raman and XPS spectroscopy. In the catalyst reduced in H 2 at 800 °C, Re is present as a nonuniform phase consisting of metallic particles with sizes of 1–4 nm and a certain amount of very small clusters (below 1 nm) undetectable by TEM. Oxidation at room temperature causes dissociative chemisorption of oxygen on rhenium with possible formation of a superficial oxide on the Re particles and complete oxidation of the clusters to Re 4+–Re 7+ species. After oxidation at 150 °C only 2% of total Re remains in the reduced state which implies high affinity of highly dispersed Re to oxygen. At 200–300 °C, oxidation of Re hastens giving a mixture of Re 4+, Re 6+, and Re 7+ ions, while at 500 °C, complete oxidation to Re 2O 7 occurs. At elevated temperatures, Re 2O 7 sublimates and instantaneously adsorbs on γ-alumina surface as monomeric ReO 4 species. At 500–800 °C, these species are strongly bound to alumina forming a kind of a surface compound with an Al–O–ReO 3 structure. This accounts for the low loss of Re observed even at 800 °C. Redispersion of rhenium was observed after a mild H 2 treatment of the oxidized rhenium catalyst.