Abstract: A mild hydrocracking catalyst contains amorphous matrix, zeolite, at least one metal compound selected from Group VIB and at least one metal compound selected from Group VIII. The catalyst is characterized in that the incorporated REUHP zeolite has dual pore distribution at <20 .ANG. and around 200 .ANG. and 3-10 percent by weight lanthanum, cerium, or mixed rare earth oxide. The amorphous matrix is .gamma.-Al.sub.2 O.sub.3 in which 80% total pore volume is contributed by pores having a diameter larger than 50 .ANG. and 60% total pore volume is contributed by pores having a diameter in the range of 50-100 .ANG.. A phosphorus promoter may be incorporated into the catalyst of this invention. The atom ratio of VIII/(VIII+VIB) in the catalyst is in the range of 0.2-0.8. The catalyst of this invention is especially suitable for one-stage once-through mild hydrocracking of heavy oil boiling above 350.degree. C. The tail oil boiling above 350.degree. C. is a high-quality feedstock for steam cracking.