Re-Co/Al2O3 (M) bimetallic catalysts were prepared by ball milling in a high-energy shaker mill using a WC container and four WC balls. The structure and activity of the Re-Co/Al2O3 (M) are compared to a Re-Co/Al2O3 (IM) sample prepared by the incipient wetness technique. The mechanically treated sample contains disordered, probably partly amorphous metal particles. Heat treatment of the Re-Co/Al2O3 (M) sample was carried out in hydrogen at 450 and 650 degreesC. It affects the crystallinity and the catalytic properties of the metal particles. The rate measured for the CO hydrogenation over Re-Co/Al2O3 (IM) catalyst is significantly higher than that measured over the Re-Co/Al2O3 (M) sample. On the other hand, in the CH4 conversion to higher hydrocarbons, the Re-Co/Al2O3 (M) showed higher activity after treatment at 650 degreesC. The opposite behavior of the M and IM samples is explained by the changing morphology of the active sites responsible for the two different reactions.