When a Zn wire was heated by electric current, ZnO whiskers grew on the wire surface. The average diameters of the whiskers grown under O-2, 20% O-2 and Ar atmospheres were 0.12, 0.17 and 0.4 mum, respectively. The well-known visible emission was observed from the whiskers grown under O-2 and 20% O-2 atmospheres. The whiskers grown under Ar atmosphere showed strong ultraviolet (UV) emission. X-ray diffraction measurements revealed that the crystalline quality of the whiskers increased with decreasing O-2 concentration in the growth atmosphere. It was found that residual O-2 Of less than 10 ppm in Ar atmosphere is used for the synthesis of the whiskers with UV emission. Monitoring O-2 concentration during the electric current heating of Zn wire in Ar atmosphere was effective in estimating the yields of the whiskers. (C) 2004 Elsevier B.V. All rights reserved.