Large, high-quality crystals of undoped and Zn-doped CuO have been prepared successfully by the floating-zone technique. Formation Of Cu2O during the crystal growth of CuO has been eliminated under optimal growth conditions for the first time. The size of the grown crystals is typically 5-7 cm length and 8-9 turn in diameter, although with Zn doping the single crystal grains are found to form less readily. The Neel temperature is found to decrease with increasing Zn doping. Magnetic hysteresis measurements did not show any irreversible behaviour in either high purity ZnxCu1-xO crystals or polycrystalline CuO. (C) 2002 Elsevier Science B.V. All rights reserved.