Influence of intrinsic electron traps on the electrical conductivity of thermochemically reduced yttria-stabilized zirconia has been studied. The defect structure of the reduced samples was characterized using optical absorption and EPR techniques. Electrical conductivity of samples containing T and C-defects have been measured by impedance spectroscopy between 500 and 1000 K. A thermally activated electronic conduction at low temperatures two orders of magnitude higher than the ionic conduction has been associated with the presence of C-traps. Evidence is given for the existence of a defect band at approximate to 1.3 eV below the conduction band. An energy level diagram comprising this band and the energy levels of T- and C-traps is proposed to explain the electronic conduction behaviour of reduced zirconia.