The product distribution for the reaction of HO2 with ClO has been studied by a discharge flow/mass spectrometry/resonance fluorescence apparatus. The upper limits of the reaction channel producing HCl+O3 are 1.5% at 298K and 3.0% at 248K. The reaction product, HOCl, in the other channel, HOCl+O2, has been detected. The reaction proceeds mainly through this channel.