A process for the alkylation of aromatic compounds with an olefin or alkyl halide having from 1 to 24 carbon atoms utilizes a novel catalyst comprising: a) a refractory inorganic oxide, b) the reaction product of a first metal halide and bound surface hydroxyl groups of the refractory inorganic oxide, c) a second metal cation, and d) optionally a zerovalent third metal. The refractory inorganic oxide is selected from the group consisting of alumina, titania, zirconia, chromia, silica, boria, silica-alumina, and combinations thereof and the first metal halide is a fluoride, chloride, or bromide of aluminum, gallium, zirconium, or boron. The second metal cation is selected from the group consisting of: monovalent metal cations in an amount from 0.0026 up to about 0.20 gram atoms per 100 grams refractory inorganic oxide for lithium, potassium, cerium, rubidium, silver, and copper, and from 0.012 to about 0.20 gram atoms for sodium; and alkaline earth metal cations in an amount from about 0.0013 up to about 0.01 gram atoms per 100 grams of refractory inorganic oxide for beryllium, strontium, and barium, and in an amount from about 0.004 up to about 0.1 gram atoms per 100 grams support for magnesium and calcium, or combinations thereof. The third metal is selected from the group consisting of platinum, palladium, nickel ruthenium, rhodium, osmium and iridium, and any combination thereof. These novel catalysts are effective in other alkylation reactions including motor fuel alkylation.