This article presents data on the hydrodesulfurization of heavy coker gasoils, a distillate from the tar obtained in the thermal cracking of resid, heavy vacuum gasoil (350-520/sup 0/C), and blends of these stocks in various ratios. A single-pass flow unit was used with a fixed bed of commercial alumina-cobaltmolybdenum catalyst. Hydrodesulfurization of the gasoils was studied at temperatures of 360-400/sup 0/C, feedstock space velocities of 0.7-1.5h/sup -1/, a pressure of 5 MPa, and a hydrogen circulation ratio of 800 m/sup 3//m/sup 3/. The heavy gasoils obtained in destruction processes were hydrodesulfurized in blends with heavy vacuum gasoil (350-520/sup 0/C) in weight ratios of 70:30 and 50:50. It is determined that dilution with the heavy vacuum gasoil (350-520/sup 0/C) has very little effect on the conditions for hydrodesulfurization of a feedstock of secondary origin. The degree of hydrodesulfurization shows a slight increase only when the distillate from the cracked tar is diluted in a 50:50 weight ratio. When the coker gasoil is diluted with a light vacuum gasoil (350-478/sup 0/C), the same degree of desulfurization is achieved with a 70:30 dilution ratio and a hydrotreating temperature of 380/sup 0/C. The primary coke-forming components in the examined feedstocks are polycyclic aromatic hydrocarbonsmore » and resins. Includes 3 tables.« less