A process for preparing a hydrocarbon conversion catalyst that comprises a specially made silica-alumina composition and a metal or metal compound selected from Group VIB and Group VIII metals. The silica-alumina composition is made by preparing an aqueous mixture containing aluminum sulfate followed by adding alkali metal aluminate to the mixture to inhance the pH to within specified range and then adding aluminum sulfate to the mixture to lower the pH. Then alkali metal silicate is added followed by several other pH swings to provide a mixture containing silica-alumina. The resulting mixture is treated with an alkaline solution to provide a precipitate solid that is recovered to obtain a silica-alumina composition containing of from 30 to 70% wt silica and of from 70 to 30% wt of alumina.