Fine ZnO particles with high crystallinity were obtained by hydrothermal synthesis under supercritical conditions. Zinc nitrate aqueous solution was pressurized to 30 MPa at room temperature and rapidly heated to 390 degreesC by mixing with supercritical water and then fed into a tubular reactor. The ZnO whiskers were prepared when the concentration of solution was below 0.02 mol/l. Room temperature photoluminescence spectrum of this whiskers showed a strong ultraviolet light emission with broad red light emission. (C) 2004 Elsevier B.V. All rights reserved.