The reaction rates were detd. at 210-460 DegK using time-resolved resonance absorption to monitor the removal of OH radicals following their creation by flash photolysis of mixts. contg. H2O or N2O + H2. An Arrhenius plot was obtained for the reaction of OH with CO, and the rate const. showed a small pos. temp. dependence. Curvature in the Arrhenius plot was predicted above 500 DegK. The rate consts. for the primary reactions of OH with C2H4 and C2H2 increased slowly, but linearly, with temp.