Hydrothermal synthesis of zinc oxide fine particles from zinc salt (Zn(CH3COO)(2), ZnSO4, Zn(NO3)(2)) and alkali metal hydroxide (LiOH, KOH) aqueous solution was carried out with a Ti alloy batch reactor in supercritical water. Particle size synthesized in LiOH solution was relatively smaller than that in KOH. Emission spectra of the particle produced from ZnSO4 and LiOH aqueous solution shows the highest intensity among these systems. Hydrothermal synthesis of zinc oxide fine particles from Zn(NO3)(2) and LiOH solution was also carried out with a flow-through apparatus for continuous production and rapid heating of the starting solution to supercritical states. Nanoparticles having an average particle diameter of 16 nm was produced at 659 K and 30 MPa. (C) 2003 Elsevier B.V. All rights reserved.