Solid state devices based on Cu2O are found to exhibit different current-voltage (I-V) relations. Though these devices have been known for almost 80 years they are still not fully understood. The standard interpretation of these I-V relations is by assuming Schottky barriers to exist between a metal electrode and the oxide. We here report on a new form of I-V relations that we have measured for devices based on thin films of Cu2O. Their interpretation calls upon mixed ionic electronic conduction in the oxide. The ionic conductivity, though low, is sufficient to allow a redistribution of the native acceptors on the time scale of the measurements, thereby affecting the electronic current carried by holes. Any contribution to the I-V relations from Schottky barriers is not significant. (C) 2004 Elsevier B.V. All rights reserved.