We report results of two-color resonant four-wave mixing experiments on highly predissociated levels of the methylthio (or thiomethoxy) radical C H3 S in its first excited electronic state Ã A12. Following photolysis of jet-cooled dimethyl disulfide at 248 nm, the spectra were measured with a hole-burning scheme in which the probe laser excited specific rotational transitions in band 33. The spectral simplification afforded by the two-color method allows accurate determination of line positions and homogeneous linewidths, which are reported for the C-S stretching states 3v (v=3-7) and combination states 11 3v (v=0-2), 21 3v (v=3-6), and 11 21 3v (v=0,1) involving the symmetric C H3 stretching (v1) mode and the C H3 umbrella (v2) mode. The spectra show pronounced mode specificity, as the homogeneous linewidth of levels with similar energies varies up to two orders of magnitude; v3 is clearly a promoting mode for dissociation. Derived vibrational wave numbers ω1′, ω2′, and ω3′ of the Ã state agree satisfactorily with ab initio predictions.