Residue hydrocracking catalysts containing 0%, 15%, 20%, 25%, and 30% of a nonconventional alumina component that has very large (0.1-100 mu m) macropores (MAP) were prepared. Their performance was compared with a commercial bimodal catalyst that was used as a standard. When compared to the standard reference catalyst and the other MAP catalysts, the 15% macropore (MAP) alumina catalysts produced greater +525 degrees C conversion, greater yields of distillates, and greater total product HDS, HDN, HDM, and MCR conversions. The +525 degrees C conversions of several MAP catalysts exceeded that obtained in a thermal experiment without a catalyst. This indicates that the properties of a residue hydrocracking catalyst can enhance conversions beyond that obtained by thermal reactions alone. All of these effects were correlated with the mesopore surface area of the used catalysts. This was the surface area of the catalyst in its working state which was contained in pores large enough for residue molecules to enter. For the cracking reaction (+525 degrees C conversion) the presence of macropores in the catalyst diminished the influence of diffusion, so that the MAP catalyst results correlated with surface area. For the hydrogenation reaction (WC ratio) the MAP catalyst results also correlated with surface area. However, catalysts with micropores produced larger WC ratios. Hydrogen, dissociated in the micropores, may have reacted with small hydrogen transfer molecules (naphthalene-tetralin) which may have transferred the hydrogen to residue molecules outside of the micropores. The additional hydrogenation in micropores may have compensated for diffusional restrictions. For the MAP catalysts, the other reactions HDS, HDM, and MCR conversion, showed the same trends as the WC ratio, suggesting that hydrogenation was the rate-limiting step for these reactions.