Three zirconia-based composite reversed-phase high-performance liquid chromatography supports with exceptional alkaline stability are described. The first support was prepared by chemical vapor deposition of carbon onto a porous zirconia substrate; the second by hydrogen treatment of the carbon coated zirconia particle at elevated temperature and the third by deposition and cross-linking of a hydrophobic polymer layer over the carbon-coated zirconia particle. The alkaline stability, and chromatographic selectivity, efficiency and loading capacity of these packing materials were examined and compared. Hydrogen treatment of the carbon particles served to remove or modify high-energy adsorption sites on the carbon surface. The polymer coating on the carbon particles increased the chromatographic efficiency and loading capacity over that of the bare carbon supports. These materials appear to be indefinitely stable at 80°C in a mobile phase of methanol-water (50:50) buffered at pH 12.