The ethanol steam reforming has been investigated over supported cobalt catalysts at atmospheric pressure. About 12% cobalt was supported on Al 2 O 3 , SiO 2 and TiO 2 , and a commercial Ni/Al 2 O 3 catalyst (G90B) was included for comparative purposes. The selectivity was found to depend strongly on the support, especially at low and medium temperatures. The initial activity of the cobalt catalysts correlated well with the metal dispersion. Acetaldehyde was an important C-containing product at low temperatures, whereas at high temperatures CO, CO 2 and CH 4 dominated the product spectrum. A significant production of ethene was observed, especially on the alumina-supported catalysts. The results are in agreement with a mechanism involving acetaldehyde as an intermediate in the steam reforming. At high temperatures ([550°C) the conversion was complete and the product distribution approaches the equilibrium. The H 2 yield approached 5 moles H 2 /mole ethanol converted, which is close to the maximum according to thermodynamic calculations. The aluminasupported catalysts (both Co and Ni) showed acceptable deactivation rates, but high carbon formation.