Measurements of the 9.6- and 10.6-μ CO2 laser transition probabilities and optical cross sections have been made by using a tuneable CO2 laser and room-temperature absorption cell. In order to increase the accuracy of the resulting constants, two measurements, one in the combined Doppler-and pressure-broadened regime and one in the pure pressure-broadened regime, provided data for the simultaneous solution of the transition rate and cross section. The 10.6-μ results are in general agreement with previous studies and knowledge of the 9.6-μ values permits performance predictions and quantitative use of gain data in this laser band.