A Fourier transform infrared study has resulted in the first observation of a vibrational spectrum of the linear SiCCH radical produced by trapping the products of the vacuum ultraviolet photolysis of a mixture of SiH4 silane, and C2H2 acetylene, in an Ar matrix at 10 K. Two fundamentals have been observed, the v(2)(sigma), carbon-carbon stretching mode at 1989.8 cm(-1) and the v(3)(sigma), silicon-carbon stretching mode at 636.0 cm(-1). The frequency of the 1989.8 cm(-1) band and the results of extensive measurements of D and C-13 isotopic shifts are in good agreement with the predictions of new CCSD(T) (coupled cluster with single, double, and triple excitations) ab initio calculations for the v(2) mode, while the assignment of the 636.0 cm(-1) band is considered somewhat less certain.