Determination of the sign of the majority charge carriers in pyrite thin films has become a difficult task due to the contradictory results obtained by thermoelectric methods and Hall coefficient measurements. An explanation for this behaviour is proposed on the basis of calculations accomplished by considering a two band conduction mechanism operating in the films. Point lattice defects, generated during the film growth, are considered as donor and acceptor states. (C) 2003 Elsevier Science B.V. All rights reserved.