Microwave-induced plasma discharge behavior of beta-SiC whiskers prepared by thermal decomposition of a sulfur containing silicon oil has been investigated in different surrounding gases. The undoped whiskers prepared in this study were white and woolly, and exhibited amazingly high electrical conductivity of 10(2) to 10(3) S cm(-1), comparable to that of carbon fibers. The undoped whiskers were brought to a red heat and emitted a strong light upon microwave irradiation in an air environment and even in flowing air at 1.01 x 10(5) Pa. Spectral analysis of the light has revealed the generation of nitrogen plasma in addition to heat radiation. In contrast, a long and narrow streak of strong bluish white light was generated from the whiskers upon microwave irradiation in flowing argon at 1.01 x 10(5) Pa, and was confirmed as an Ar plasma based on the 4s-4p electron transition of Ar atoms. It was found that the plasma streak was stable even in an atmosphere of flowing argon containing a small amount of trichloroethylene, oxygen, and water vapor. Generation of such a microwave-induced plasma discharge in air and an Ar plasma streak were unique phenomena with beta-SiC whiskers and carbon fibers exhibiting high electrical conductivity. Decomposition of trichloroethylene in air by the plasma discharge was less effective than thermal decomposition from the standpoint of conversion of trichloroethylene and the amounts of partial decomposition products. However, trichloroethylene could be completely decomposed by the Ar plasma streak with low energy consumption, demonstrating the potential advantage of a microwave-induced Ar plasma streak to decompose toxic halogenated hydrocarbons.