Aluminum oxide (A2O3) particles were collected from the space shuttle exhaust plume immediately following the launch of STS-34 on October 18, 1989. A2O3 samples were obtained at 2.4, 3.0, 3.2, and 7.4 km in altitude. The samples were analyzed using scanning electron microscopy to develop particle size distributions. There were no indications that the particle size distribution changed as a function of altitude. The particle number concentrations per cubic meter of air sampled (NC) for the four collections was found to fit the exponential expression NC=(3.2¿108)10-0.89d, where d is particle diameter in micrometers, over the interval of 0.3--7 μm. The mass median diameter for this distribution occurred at about 4 μm. ¿American Geophysical Union 1991