We have studied the atomic structure of the Ga-stabilized GaAs(001)-c(8 x 2) surface using rocking-curve analysis of reflection high-energy electron diffraction (RHEED). The c(8 x 2) surface is stable only at temperatures higher than 600 degreesC, but changes to the (2 x 6)/(3 x 6) structure at lower temperatures. The atomic structure of the c(8 x 2) surface at high temperatures is basically the same as that determined by the analysis at room temperature. We propose that the surface atomic configurations are locally fluctuating at high temperatures. (C) 2003 Elsevier Science B.V. All rights reserved.