Air and water concentrations of methyl bromide (CH (sub 3) Br) and methyl chloride (CH (sub 3) Cl) were measured in the Southern Ocean from late October through mid-December 2001. The minimum degradation rate constants needed to maintain these saturation anomalies are consistent with the observed total degradation rate constants, suggesting that there is no significant production of these gases in this region. (mod. journ. abstr.)