The rate constant for absorption of carbon dioxide into water increases as the stirring rate of the water is increased up to a maximum rate and then stays constant until the stirring is sufficiently vigorous to affect the surface area. At the maximum, the change in absorption rate with gas pressure shows excellent first-order kinetics and can be interpreted in terms of reversible exchange between the gas phase and a uniform solution, without invoking the existence of a surface layer of saturated solution, A general treatment is described for extracting the rate constant for absorption of gas from the kinetic data. By comparing the rate of absorption with the rate predicted by kinetic theory, we obtain an accommodation coefficient (gamma) of(5.5 +/- 0.5) x 10(-8) at 20 degrees C. Absorption rates measured in solutions of sodium chloride decrease with increasing ionic strength. We note an approximately linear relationship between log gamma and log s, where s is the gas solubility at 1 atm.