The laser/flash photolysis-resonance fluorescence technique was employed to study the kinetics of the reaction OH+COS→products. Complicating secondary reactions involving COS photofragments were eliminated by using 193 nm laser photolysis of HNO3 as a source of OH. The rate constant was found to be much slower than previous measurements indicated. Based on our experiments, the upper limit for k1 at 298K is 8.8¿10-15 cm3molecule-1s-1. Our results suggest that the title reaction is only a minor COS degradation pathway in the troposphere.