The nonlinear electrical characteristics and stability against AC accelerated aging stress of Al-doped low voltage ZnO varistors were investigated as a function of Al content. The varistors with Al exhibited a high nonlinear coefficient above 30, compared with that without Al. The varistors with 200 ppm Al3+ exhibited a highest nonlinearity, with a nonlinear coefficient of 42.9 and a leakage current of 9.5 mu A. But the varistor without Al showed high stability, in which the variation rate of varistor voltage, of nonlinear coefficient and of leakage current are -4.1, -4.3 and +20.7%, respectively, under AC accelerated aging stress (1-0 V-lmA/125 degrees C/24 h). (c) 2005 Elsevier B.V. All rights reserved.