The potential radiative impact of the relatively weak 9.4- and 10.4-μm bands of CO2 is investigated. Line-by-line calculations are employed as a standard against which to compare the accuracy of laboratory data, narrow-band models, and broadband models. A comparison of the line-by-line calculations to laboratory data demonstrates that the line-by-line procedure and laboratory data typically yield comparable results; however, there are cases of substantial disagreement between the line-by-line results and the laboratory data. It is observed that the Goody narrow-band model yields band absorptances in good agreement with the reference line-by-line calculations. For application to climate models, new broadband parameterization, which are consistent with the band intensities found on the 1986 Air Force Geophysics Laboratory HITRAN data base, are presented for the 9.4- and 10.4-μm bands of CO2. Clear-sky flux calculations demonstrate that for projected increases of CO2 the impact of the 9.4- and 10.4-μm bands is comparable to that attributed to projected increases of tropospheric ozone. ¿ American Geophysical Union 1991