A simple, low-cost hydrothermal method was developed to synthesize in one step single crystals of yttria-stabilized zirconia (YSZ) nanciparticles of ca. 5 nm. Subsequent dialysis and ultrasonic dispersion afford a very stable YSZ suspension in pure water. Characterization by X-ray diffraction, transmission electron microscopy, nitrogen adsorption, and dynamic light scattering C demonstrates that the particles are single crystals of the cubic Fm3m structure with a large specific surface area of 150 m(2)/g.