The dislocation etch pits in an as-grown [0 0 0 1] direction sapphire crystal (alpha-Al-2-O-3) produced by Cz method were investigated using an environmental scanning electron microscope for the first time. The clear and stable contrast images of triangular, hexagonal, and quadrilateral etch pits were observed, which demonstrate the structural symmetry of sapphire crystal along [0 0 0 1] direction. The dislocation density we measured is 1-2 x 10(5)/cm(2) and the formation of the etch pits is also discussed. (C) 2004 Elsevier B.V. All rights reserved.