Degenerate four-wave mixing (DFWM) was used to record the spectra of charged and neutral carbon-containing radicals generated in a pulsed discharge Source within a supersonic slit-jet expansion. Detection limits of similar to 10(9) molecules cm(-3) are achieved. The DFWM method allows a selective molecular detection by varying the discharge timings. Increased spectral selectivity is obtained by applying the two-color, doubly resonant four-wave mixing variant. This shows the potential of the techniques for sensitive and selective spectral analysis of radicals in discharges. The methods are successfully used for the detection Of C4H, HC2S, and HC4H+ with signal-to-noise in the range of 10(2)-10(4).