Rate consts. and branching ratio for the reaction channels CH3 + O2 -> CH3O + O (reaction 1) and CH3 + O2 -> CH2O + OH (reaction 2) have been derived from RRKM theory by assuming a common CH3O2 intermediate. The computation is based on a 160 kJ/mol isomerization barrier between CH3O2 and CH2OOH as derived recently in direct studies of the reverse CH3O + O reaction at low temps. In contrast to most previous conclusions, reaction 2 is predicted to dominate over reaction 1 at all temps. below 2800 K.