Measurements of 10.6-μm lidar backscatter were compared with calculated backscatter based on nearly simultaneous observations of stratospheric and tropospheric aerosol size distributions. It was found that there is better agreement in the troposphere, even though the uncertainties of the calculation are greater for this region due to the variabilities in both the spacial concentration and physical makeup of the aerosol. A second comparison study was made to test the consistency of the mean tropospheric extinction values at 1.02 μm (as reported by the SAGE satellite) with the values calculated from an ensemble of 400 measured size distributions thought to be representative of mid-continental tropospheric aerosol. The two methods produce consistent results within the expected degree of uncertainty. The ensemble of 400 ''proven'' size distributions is then used to calculate a statistical relationship between the 1.02-μm extinction and the 10.6-μm backscatter. ¿1991 American Geophysical Union