The composition and microstructure of SiC whiskers from three different suppliers were studied to understand their physical and chemical properties. The following analytical meth ods were utilized : complete chemical analysis, morphological examination by scanning electron microscopy and by high-resolution transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, and thermogravimetric analysis of the oxidation rate of the three SiC whiskers at 1050 degrees C in oxygen and at 1150 degrees C in air.