The oxygen storage capacity (OSC) of CeO2-ZrO2 solid solutions that were directly formed as nanocrystals by thermal hydrolysis of acidic aqueous solutions of (NH4)(2)Ce(NO3)(6) and ZrOCl2 at 150degreesC increased from 94 mumol of O-2/g for pure CeO2 to >400 mumol of O-2/g for compositions of CeO2/ZrO2 with molar ratios (C/Z) from 74.1/25.9 to 41.7/58.3 (maximum value of 431 mumol O-2/g was reached at the composition C/Z = 51.7/48.3) and then decreased with increased ZrO2 content in the solid solutions. As compared with pure CeO2, the CeO2-ZrO2 solid solutions that contained <84.8 mol % ZrO2 maintained high specific surface area and large pore volume with nanosized pores (pore size at maximum pore volume) <10 min in diameter after heat treatment at 700degreesC.