Isomerization of heptane was carried out at 573 K under atmospheric pressure using molybdenum oxides as catalysts. MoO3 was inactive for this reaction. H-2 reduction of MoO3 at 623 K, however, enhanced the isomerization activity and selectivity, which became almost constant after the reduction for 24 h. The reduced MoO3 exhibited a higher isomerization activity than a typical bifunctional catalyst, 0.5 wt% Pt/USY zeolite, while there was no appreciable difference in product distribution between these two catalysts. These results indicate that the reduced MoO3 catalyzed the isomerization of heptane via a conventional bifunctional mechanism.