Disclosed is a process for improving the octane quality of a naphtha which process comprises contacting the naphtha, at pressures ranging from about 25 psig to about 175 psig, with hydrogen introduced at a rate ranging from about 1000 SCF/B to about 5000 SCF/B, at a temperature from about 800.degree. F. to about 1100.degree. F., and a space velocity ranging from about 1 W/H/W to about 5 W/H/W, and with a catalyst comprised of the metals platinum, rhenium, and iridium on a refractory porous inorganic oxide support, wherein the concentration of each of platinum and rhenium is at least 0.1 percent, and that of iridium is at least 0.15 percent, and at least one of said metals is present in a concentration of at least 0.3 percent, and the sum total of said metals is present in a concentration greater than 0.9 percent.