The pulsed laser photolysis--pulsed laser-induced fluorescence technique has been employed to study the kinetics of the reaction, OH+CO → k1 products, as a function of temperature and pressure in N2, air, and O2 buffer gases. At pressures of 1 atm and below, k1 is found to increase linearly with increasing pressure. Within experimental uncertainty, both the rate constant in the low-pressure limit and the slope of the k1 versus pressure dependence are found to be the same at 262 K as at 299 K. From our data we obtain the expression k1=(1.47¿0.08)¿10-13 <1+(0.59¿0.10)P> independent of temperature, where P is in units of atmospheres and k1 is in units of cubic centimeters per molecule per second. Within experimental uncertainty, the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. In 700-torr air at 299 K, k1 is found to be independent of water vapor concentration over the range 0.01--20 torr. Our results will have little effect on current panel recommendations of k1 values for use in atmospheric models. However, uncertainties in the temperature dependence under atmospheric conditions, the third body efficiency of O2, and the effect of water vapor on k1 are now greatly reduced.