The equation derived by COBURN, FORSTER, and KANE (1965) for the absorption and elimination processes of carbon monoxide was solved analytically with less-restrictive assumptions.The solution can predict the COHb levels during and after exposures of 50 to 500ppm CO not only in human subjects but also in rats and mice with reasonable accuracy, except for the CO elimination by breathing hyperbaric oxygen. Physiological parameters required for the prediction are only body mass and hemoglobin concentration.It has been shown that the rate of both processes is inversely proportional to B^0.24 in mammals, where B is the body mass: the smaller the animal, the faster the rate of both absorption and elimination.