The reaction of CH3O2 with ClO has been studied at 293 K using a flow reactor sampled by a mass spectrometer. Under conditions where [ClO] much greater than [CH3O2], the CH3O2 decayed under pseudo-first-order conditions giving a rate coefficient of (1.9 +/- 0.4) x 10(-12) cm3 s-1. CH3OCl was detected as a reaction product. The implications of the measurements for the chemistry of the stratosphere are discussed briefly.