Kinetics and mechanisms of the reactions CH3 + O -> CH2O + H (1) and CH3O2 + O -> CH3O + O2 (2) at 298 K was investigated using 193 nm laser photolysis of N2O-azomethane mixts. for the simultaneous generation of O(3P) atoms and CH3(N2 as diluent)-CH3O2 (O2 as diluent) radicals, combined with laser-induced fluorescence for the time-resolved detection of reaction products. From measurements of CH2O formation the rate coeff. k1 was detd. as k1 = (1.1 +- 0.4) * 10-10 cm3s-1. Concurrent yield studies suggest that CH2O accounts for the total loss of CH3. The rate coeff. k2 was detd. from observation of CH3O formation to be k2 = (4.3 +- 2.0) * 10-11 cm3s-1. Energy diagrams are presented which suggest that the dynamics of both reactions are detd. by primary capture mechanism forming highly vibrationally excited adducts and followed by rapid subsequent decompn. As a result of high excitation energies and low exit barriers k1 and k2 are not pressure-dependent.