The A 2A1 - X 2E fluorescence of CH 3O in solid Ar in the wavelength range 310-420 nm has been studied either by simultaneous laser photolysis and excitation of CH3ONO in the Ar matrix or by laser excitation of the products deposited from the reactions of microwave-discharged CF4 with CH3OH diluted by Ar. The spectrum showed an extensive progression in C-O stretching (v 3). The zero-phonon lines of 12CH3O and 13CH3O yielded unambiguous vibrational assignments with v00 = 31 291, ω″e = 1051, and ω″ex″e = 6.5 cm-1 for 12CH3O. Observation of several weak combination bands also yielded v″2 = 1356, v″4 = 2758, and v″5 = 1406 cm-1. The laser excitation spectra in the 273-322 nm region also exhibited an intense progression in C-O stretching with ω′e = 657 and ω′ex′ e = 4.4 cm-1 for 12CH3O. Additional wave numbers v′2 = 1308 and v′5 = 1410 cm -1 were also obtained from the combination bands.