A kinetic study of ethanol steam-reforming reaction on Rh catalyst supported over a spinel structure (MgAl2O4/Al2O3) was carried out From the analysis of products distribution, the following four reactions were proposed as the reaction scheme C2H5OH -> CO + CH4 + H-2 (ED), C2H5OH + H2O -> CO2 + CH4 + 2H(2) (ER), water gas shift reaction, and methane steam-reforming reaction When the initial rate method was applied, it was demonstrated that in the rate-determining step (RDS) two active sites of the same type are involved With use of our experimental results and data obtained from the literature, a sequence of 14 elementary steps were proposed, in agreement with the reaction scheme Taking into account both the reaction mechanism and the occurrence of two active sites in the RDS, four different kinetic expressions can be formulated in which the RDS is (1) dissociative adsorption of ethanol, (2) dehydrogenation of ethoxide (3) C-C bond scission, or (4) reaction between two adsorbed species Finally, when discrimination models were applied it was verified that the mechanism that fits experimental data is that in which the RDS is the surface reaction