Wehave performed coherent anti-Stokes Raman scattering (CARS)measurements of acetylene in a laminarCH4/C2H2/air flame. The acetyleneconcentration was determined from the ratio of the resonant acetyleneCARS signal to the nonresonant background CARS signal. The resonantand nonresonant signals were detected separately on each laser shotusing polarization analysis and a two-channel detection system. Theflame temperature profile was determined from fits of nitrogen CARSspectra. Experimental acetylene CARS spectra are compared with theoretical spectra.