Anomalous charge–voltage (Q–V) characteristics are observed for several types of alternating-current thin-film electroluminescent (ACTFEL) devices. These Q–V curves are anomalous because conduction charge flows in these devices exclusively during the portion of the wave form in which the applied voltage is constant, at its maximum value; this kind of conduction charge is denoted relaxation charge. In a normal ACTFEL device, most of the conduction charge flows during the portion of the wave form in which the applied voltage increases with time. The anomalous Q–V characteristics are attributed to insulator leakage for the devices tested. Simulation shows that such anomalous behavior may arise from either insulator or phosphor leakage.