Lattice images from molybdenum disulfide-based catalysts have been obtained by high resolution electron microscopy (HREM), in order to determine the influence of the preparation method and promoter concentration on the microstructure of the molybdenum disulfide crystallites. It was found that the mean number of {002} planes forming the crystallite is only slightly dependent on those parameters while crystal length varies significantly with them. Such results indicate that the edge area (proportional to length times number of stacking layers) is modified when the above mentioned parameters are changed. On the other hand, lattice images from {100} and {h01} showed that their structure is as highly disordered as in the case of {002} planes. The frequency of appearance of such planes was strongly modified by the evaluation test in the thiophene hydrodesulfurization reaction. © 1993, Elsevier Science & Technology.