Catalytic hydroisomerization of n-heptane was carried out following the reduction by hydrogen of bulk MoO3, MoO3/TiO2, as well as MoO3 were present on the surface of commercial bulk MoO2. A conversion of 55% and a selectivity of more than 90% in isomerization products, mainly 2- and 3-methyl hexanes, were obtained at 573 K using the supported system. The major hydrocracking products obtained are C3 and C4 with a ratio C3/C4 = 1.2. Modifications of the reactant flow rate as well as the catalyst mass, enabled us to increase the conversion to 74% with a selectivity of 82% in isomerization products at 573 K reaction temperature. The catalytic active phase is attributed to the bifunctional MoO2(H-x)(ac). single phase. The metallic function is assured by MoO2 delocalized pi electrons as identified by XPS-UPS in terms of density of state (DOS) at the Fermi-level. The Bronsted acidic functional group(s), (H-x)(ac). were deduced from the adsorption of ammonia, the isomerization of olefins at relatively low reaction temperatures in comparison to alkanes and the dehydration of 2-propanol. (C) 2003 Elsevier B.V. All rights reserved.