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It was found in a commercial single crystal superalloy CMSX-4 that preferential orientation of the gamma' rafting in dendrite core was not dependent on the sign of the applied stress sigma(A), but on the sign of the sum of the applied stress sigma(A) and a critical equivalent stress sigma(c). This critical equivalent stress sigma(c) caused by material inhomogeneity has been predicted previously; however it was first determined experimentally to be in the range 39.8-47.2 MPa in the present study. Moreover, it qualitatively demonstrated that the critical equivalent stress sigma(c) played a significant role in the creep behavior of superalloys at high temperature and low stress. (C) 2009 Elsevier Ltd. All rights reserved.