One of the least understood of the possible environmental effects from trace constituents emitted by aircraft is that of elemental carbon, soot. Distributions of soot in the troposphere and stratosphere based on emissions from current and projected fleets of aircraft are determined in this study; these distributions are then used in evaluating the resulting effects on radiative forcing on climate. The University of Illinois two-dimensional chemical transport model of the troposphere and stratosphere is used in deriving the distributions of soot. Model results for 1992 aircraft emissions generally compare well with the upper tropospheric and lower stratospheric measurements for the same year. Estimates of atmospheric soot distributions due to aircraft are also derived for roughly the year 2015, when a fleet of high-speed civil transports is assumed to be fully operational. Using the present and future distributions of atmospheric soot, direct radiative forcing estimates on climate were made with a modified version of the National Center for Atmospheric Research Community Climate Model 3 column radiation model. When compared with other forcings on climate, the determined soot distributions were found to have negligible impact. ¿ 1998 American Geophysical Union