Conversion of thiophene hydrodesulfurization has been measured on nine different, MoOx - or WOx-based, metal- (Co, Ni, Pd, Pt) -promoted, sulfided catalysts at different flow rates of thiophene. The kinetic equation of the process and an activity parameter for the catalysts was determined. The correlation observed previously between the number of exchangeable sulfur atoms in the catalysts and their HDS conversion was found to be valid by applying these activity parameter data.