Defect structures in (I 11) 3C-SiC platelets, grown using the Baikov technique, were studied using synchrotron white-beam X-ray topography and triple-axis diffractometry. The ((1) over bar(1) over bar(1) over bar) facets of the platelets were covered with a lamella of twinned single crystal less than 15 mum thick that could be imaged in reflection and transmission X-ray topographs. Rocking curves of the twin lamella were broadened, while X-ray topographs of the crystals' bulk matrixes showed the matrixes were of nearly perfect crystal. Stacking faults on the (I 1 1) habit planes were observed in topographs of the bulk of the crystals; these always persisted into the topographs of the twin lamellae. Inclusions occurred near the composition plane of the twin lamellae. Open-ended stacking fault tetrahedra were also noted. (C) 2003 Elsevier B.V. All rights reserved.