We have investigated current-voltage(I-V) characteristics of organic light-emitting diodes based on TPD/Alq(3) organics depending on the application of forward-reverse bias voltage. Luminance-voltage characteristics and luminous efficiency were measured at the same time when the I-V characteristics were measured. We have observed that the I-V characteristics shows a current mxima at low voltage, which is not related to the emission from Alq(3).