The characterization of cobalt molybdenum nitrides with various cobalt contents has been studied using XRD, TEM, XPS, and temperature-programmed reactions with NH3. The hydrodesulfurization of thiophene on the cobalt molybdenum nitride was carried out using a differential microreactor at atmospheric pressure. The XRD analysis of Co(50)973 indicated that CO3Mo3N was formed from the nitriding of a CoMoO4 precursor prepared from Co(NO3)(2). 6H(2)O and (NH4)(6)Mo7O24. 4H2O but not from the mixture of CoO and MoO3. Co-(10-25)973 had a high surface area of 120-129 m(2) g(-1), but Co(50)973 had that of 12 m(2) g(-1). The BET surface area was related to the molybdenum ions (Mo2+ and Mo3+) and cobalt ion (Co3+) in the bulk sample. The XPS and elemental analyses of Co(50)973 showed that the bulk composition was CO3MO3N .N-0.2 and the surface composition was Co3Mo3N .N-2 The cobalt molybdenum nitride Co(0-35)973 was more active than cobalt molybdenum sulfide an basis of catalyst weight in the hydrodesulfurization of thiophene at 623 K.