AN ADVANTAGEOUS HYDROGEN SUPPLY SYSTEM IS DISCLOSED FOR THE HYDROGENATION OF CERTAIN UNDESIRABLY AROMATIC PRODUCT FRACTIONS DERIVED FROM HYDRCRACKING SYSTEMS, WHEREBY ESSENTIALLY THE SAME EQUIPMENT AND POWER REQUIRED TO SUPPLY MAKEUP HYDROGEN TO THE HYDROCRACKING SYSTEM IS USED TO CIRCULATE HYDROGEN ONCE-THROUGH THE POST-HYDROGENATION SYSTEM, THEREBY ELIMINATING THE NEED FOR SEPARATE MAKEUP AND RECYCLE GAS COMPRESSORS FOR THE LATTER. DUE TO THE RELATIVELY HIGH CHEMICAL HYDROGEN CONSUMPTION IN THE HYDROCRACKING SYSTEM, AND THE RELATIVELY LOW FEED RATE AND MILD CONDITIONS IN THE HYDROGENATION SYSTEM, IT IS FOUND THAT THE MULTI-STAGE MAKEUP GAS COMPRESSOR REQUIRED FOR THE HYDROCRACKING SYSTEM CAN BE ADVANTAGEOUSLY UTILIZED TO MOVE THE MAKEUP HYDROGEN REQUIRED FOR THE HYDROCRACKER FIRST THROUGH THE HYDROGENATION SYSTEM, AND THAT SUCH MAKEUP HYDROGEN IS FORTUITOUSLY SUFFICIENT TO OPERATE THE HYDROGENATION SYSTEM IN ONCE-THROUGH FASHION, I.E. WITHOUT RECYCLE.