During the GATE observational program, aircraft radiative flux measurements were taken at several altitudes in the Saharan dust. On the basis of these flux measurements at 28 wavelengths in the 0.4-0.9 μm wavelength region, the corresponding vertical particle size spectra have been inferred. These particle size distributions, calculated by using spherical Mie theory, have been represented by quadramodal combinations of gamma functions. The calculated quadramodal size distributions were characterized by mode radii at 0.1, 0.2, 1.0, and 2.0 μm, with a relatively narrow spread of particle sizes centered about each mode radius. The number density of the smallest particle mode was found to increase with increasing height, while that of the largest particle mode decreased with increasing height. Comparison of deduced particle sizes of a ''dusty'' day (September 4) and a ''clear'' day (August 13) showed that the dusty day was characterized far more by the presence of large particles than by an increase in small particle concentration. Heating rates as large as 0.4¿C/hour μm were found for September 4, 1974.