By impedance spectroscopy analysis, the conduction mechanism of the organic semiconductor of tris-(8-hydroxyquinolate)-aluminum (AlQ(3)) is studied. Equivalent circuit analysis was performed with a series resistance and a pair of a parallel capacitance and a parallel resistance. It is found that the conduction mechanism seems to be space-charge limited current with exponential trap distribution, and the dielecric relaxation time of the material is decreased dramatically with increasing applied bias voltages. (C) 2004 Elsevier B.V. All rights reserved.