Measurements of the 9.6‐ and 10.6‐&mgr; CO2laser transition probabilities and optical cross sections have been made by using a tuneable CO2laser 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‐&mgr; results are in general agreement with previous studies and knowledge of the 9.6‐&mgr; values permits performance predictions and quantitative use of gain data in this laser band.