Several topical results of electron microscope analyses for microstructures in epitaxial lateral overgrown (ELO)-GaN are reported. (1) Dislocations lying on (000 1), or horizontal dislocations (HDs), are generated in ELO-GaN layers overlying on a mask of a-SiO2. The HDs have a shape of loop or semi-loop, and the morphology suggests that the HDs are generated through a multiplication mechanism with the assistance of internal stress. (2) On GaInN/GaN, a pit is formed at the end of a threading dislocation (TD) of any Burgers vector, a, e or a+c. The density and distribution of TDs in ELO-GaN can be estimated by observing these growth pits after a subsequent deposition of a thin GaInN layer on the ELO-GaN. The critical thickness for the formation of pits has a dependency upon the concentration of In in GaInN and the Burgers vector. (3) It was demonstrated that electron backscattering diffraction pattern (EBSP) analyses can estimate a two-dimensional distribution of c-axis orientation of ELO-GaN for a wide area with an accuracy of 0.2degrees or better. (C) 2002 Elsevier Science B.V. All rights reserved.