We have studied the cracking behavior of oxide scales developed on high purity nickel single crystal during creep deformation under oxygen at 550degreesC. The oxide microstructure exhibits a network of parallel cracks with a constant spacing between cracks. The deterioration of the oxide scale is monitored by acoustic emission. The creep deformation mechanisms with oxide scale are investigated and compared to vacuum creep experiments. Differences in creep behavior between these two atmospheres are obvious. This study is followed by a stress relaxation analysis. The acoustic emission technique provides a large number of results for the understanding of damage of the oxide scales during creep deformation at 550degreesC. (C) 2003 Kluwer Academic Publishers.