The preparation of bulk MoVTe(Sb)Nb mixed oxide catalysts using a traditional slurry method, results in highly active catalysts for oxidative dehydrogenation of ethane to ethene. Several major phases including orthorhombic M1, hexagonal M2 or MoxM1-xO2.8 (M = V or Nb) have been detected in the catalysts from characterization results such as X-ray diffraction (XRD), SEM and EDX analyses. Ethane conversion and yield to ethene increase with increasing content of the M1 phase in the catalysts. The maximum yield of ethene (ca. 87% selectivity and ca. 90% conversion, STYC2H4 of 176 gkg(cat)(-1)h(-1)) has been obtained with a MoV0.31Te0.2Nb0.14 mixed oxide catalyst, calcined at 873 K under nitrogen, containing almost pure orthorhombic M1 phase and small amounts of unidentified impurity phases, operating at a relatively low reaction temperature of 673 K. The orthorhombic M1 phase has been shown to be the most active in ethane activation and the most selective for ethene formation. The hexagonal M2 phase is relatively inactive in ethane activation and less selective for ethene formation. The Te-free phases such as Sb4Mo10O31 and MoxM1-xO2.8 (M = V or Nb) show the lowest selectivity to ethene. (c) 2005 Elsevier B.V. All rights reserved.