The origin of the round pinholes, ranging 30-70 mum in diameter, in indium-tin-oxide (ITO) thin films on the glass substrates were investigated. It has been found that the round pinholes in ITO thin films might arise from the tiny particles and organics, adsorbed onto the residual water of imperfectly pre-dried glass substrates at the pre-drying bath. The tiny particles and organics on the glass substrates might cause to weaken the adhesive powers between the ITO thin films and the glass substrates, finally resulting in the round pinholes at the photopatterning process. By Taguchi methods, it was revealed that the generation of the round pinholes in ITO thin films was directly related to the temperature and the amount of heat supply at the pre-drying bath. A simplified mechanism on the formation of the round pinholes in ITO thin films is proposed and verified. (C) 2003 Elsevier Ltd. All rights reserved.