A series of mixed Pt-promoted monoclinic and tetragonal sulfated zirconia catalysts were prepared and characterized. The catalysts contained 27-86% of the monoclinic phase. The zirconia samples were prepared by varying the speed of precipitation of the hydrous zirconia and the pH of the final solution. The hydrous zirconia was then calcined prior to promotion with Pt and sulfate. The catalysts were activated just prior to activity studies with n-hexadecane. This synthesis route and pretreatment produced mixed-phase catalysts which yielded comparable conversion and selectivity data to that of a purely tetragonal catalyst using optimum conditions. The data show that an active catalyst can be obtained with the monoclinic phase present and that addition of sulfate after development of the crystalline phases can yield an active catalyst.