A comparison of several measurements of the size distribution for tropospheric aerosols in which soil-derived aerosols are significant shows that these aerosol size distribution appear to be characterized by a common mode structure, with the optically important soil particles having radii between 0.5 and 10.0 μm. These measurements suggest that under conditions of low dust loading a reasonable characterization of the size distribution for soil-derived aerosols is a log normal distribution with a surface mean radius of 1.5 μm and a geometric standard deviation of 2.2.