The reactions of OH with H2 and CO were studied by the flash-photolysis-kinetic-spectroscopy technique over the temperature range 300-500°K. At both ends of this range it was verified that the reactions are first order in [OH] and [H2] or [CO]. The Arrhenius parameters and their 95% confidence limits, as determined from least-squares fits of the data, follow: For H2+OH→H+H2O, E=4020±180 cal/mole and ogA (cc/mole·sec) =12.61±0.10; for CO+OH→CO 2+H, E= 230±140 and Iog A = 11.10±0.07.