Samples of MoO3/γ-Al2O3 with different MoO3 loadings (8, 12 and 16 wt%) calcined at different temperatures (800, 950 and 1100 K) have been used in the transesterification of sunflower oil with methanol. Activity was the highest when the samples were calcined at 950 K, the most active catalyst being 16%MoO3-Al 2O3. XRD and Raman spectroscopy reveal the presence of many Mo-phases, such as dispersed surface molybdenum specie, bulk MoO 3 and Al2(MoO4)3 in the samples. The influence of various parameters, such as Mo-loading, calcination temperature, reaction temperature and mole ratio of reactants (methanol:oil), on the reaction is presented. The reaction studies have been carried out both in a batch reactor and in a fixed-bed flow reactor. The studies reveal that a sound fixed-bed continuous transesterification process for the production of biodiesel can be designed using MoO3-Al2O3. © 2011 Elsevier B.V. All rights reserved.