Active carbon supported molybdena catalysts (15% MoO3) were prepared by new slurry impregnation method (SIM) using carbon of various origin and particle size. The support was refluxed with the slurry of powdered MoO3 in water. A low solubility of MoO3 was sufficient for transport of MoO3 from the powder via the solution to the surface of the support. Calcination was left out because no other chemicals beside MoO3 and water were used in the impregnation. The catalysts were presulfided and tested in hydrodesulfurization of thiophene at 1.6 MPa and 300-400-degrees-C. Their activity was four times higher than that of a commercial molybdena on alumina catalyst and about the same as the activity of a carbon supported catalyst prepared by the conventional impregnation method (CIM) using ammonium heptamolybdate. The advantage of the new SIM over CIM method is : (i) all molybdena species are deposited by adsorption; precipitation during drying is negligible, (ii) oxidative degradation of the carbon support cannot occur during preparation because calcination is left out; ammonium sulfide is not formed during presulfidation of the uncalcined catalysts.