Indium-tin-oxide (ITO) coated on a glass plate as the transparent electrode in polymeric light-emitting diodes (LEDs) generates some volcano-like patterns during use especially at a higher applied electric field strength. Such an ITO damage phenomenon is independent of Joule heat, conjugation structure of the polymer, and light-emission process, but only dependent on the applied electric field strength. The ITO damage, which results from a self-decomposition reaction, can cause a reduction of lifetime of the device. (C) 1996 American Institute of Physics.