A catalytic hydrocracking process which comprises: (a) contacting a hydrocarbonaceous feedstock having a propensity to form heavy polynuclear aromatic compounds and a liquid recycle stream in a hydrocracking zone to convert a substantial portion of the hydrocarbonaceous components in the feedstock to lower boiling products; (b) recovering a hydrocarbon effluent from the hydrocracking zone and partially condensing the hydrocarbon effluent from the hydrocracking zone and separating the same into a lower boiling hydrocarbon product stream and an unconverted hydrocarbon stream having at least a portion boiling above about 400.degree. F. (204.degree. C.) and comprising trace quantities of heavy polynuclear aromatic compounds; (c) introducing at least a portion of the unconverted hydrocarbon stream into a hydrogen stripping flash zone with a first hydrogen-rich gaseous stream having a temperature greater than the hydrocarbon stream at flash conditions thereby increasing the temperature of the hydrocarbon stream and vaporizing at least a portion thereof to produce a vapor stream comprising hydrogen and hydrocarbon compounds and produce a liquid hydrocarbon stream comprising heavy polynuclear aromatic compounds; (d) contacting the vapor stream comprising hydrogen and hydrocarbon compounds with a hydrogenation catalyst in a hydrogenation reaction zone to increase the hydrogen content of the hydrocarbon compounds contained in the vapor stream; (e) condensing at least a portion of the resulting effluent from the hydrogenation reaction zone to produce a second hydrogen-rich gaseous stream and a liquid stream comprising hydrogenated hydrocarbon compounds; and (f) recycling at least a portion of the liquid stream comprising hydrogenated hydrocarbon compounds recovered in step (e) to the hydrocracking zone in step (a).