This study was carried out to develop a new preparation process for porous alumina-zirconia by the sol-gel method and to examine their porous properties. The gelation of alkoxides by the sol-gel method was used for the formation of a precursor composed of an alumina-zirconia netwook structure. By this process, porous alumina-zirconia with a large surface area (> 300 m(2)/g), a very small pore size (0.5-0.9 nm) and a small pore size distribution was prepared. The porous properties of these materials were dependent upon the zirconia content. The optimum ratios of raw materials forming the gels are C2H5OH/Al(OC4H9)(3) = 100/1, Al(OC4H9)/H2O = 2/1, Al(OC4H9)(3)/HNO3 = 20/1, Zr(OC4H9)(4)/H2O = 4/1 (in moles), which gives a transparent gel and shortest gelation time.