Modified industrial alumina-nickel-molybdenum catalysts manufactured by OOO NZK have been tested in the mode of hydrotreating of heavy vacuum gas oil on a pilot plant of OAO Middle Volga Research Institute of Oil Refining (OAO SvNIINP). A change in hydrocarbon-type and structural-group composition of gas oils during the hydrogen treatment process has been considered. It has been found that hydrotreating on the GR-24M, NKYu-300, and NKYu-330 catalysts under the examined conditions (340-400A degrees C, 4.0 MPa, 0.5-1 h(-1), hydrogen: feedstock ratio of 500-800: 1 Nm(3)/m(3)) leads to a reduction in sulfur, nitrogen, and metal contents of the gas oil and to saturation of polyaromatic compounds with hydrogen, thereby facilitating the further destruction of the feedstock in a catalytic cracker.