Aluminium oxide samples from the exhaust of space shuttle launches STS-1, STS-4, STS-5, and STS-6 were collected from surfaces on or around the launch pad complex and chemically analyzed. The water-soluable fraction, &rgr;H, acid-soluble fraction, and insoluble fraction were determined for each sample. X ray diffraction analysis of the insoluble particulate (always >72% of the sample weight) indicated that these fractions wre α-Al2O3 and thus confirmed that the six samples analyzed were space shuttle alumina. Electron miroscopic examination of the particles revealed spherical morphologies with diameters ranging from about 1 to 25 μm. Calcium, magnesium, potassium, ammonium, and sodium ions were measured as indicators of the amount of ground debris or sea-salt particles incorporated into the samples. All samples analyzed contained significantly elevated amounts of water-soluble chloride and aluminium (III) ion. Results from these analyses, and from laboratory experiments in which calcination-produced aluminas were exposed to gaseous HCl and H2O mixtures from room temperature to 200¿C, suggest that the surface of the shuttle exhaust alumina particulates should be viewed as haing more of the characteristics and properties (e.g., hydrophilicity) of aluminium chlorides and oxychlorides than of aluminium oxides. Since our collection techniques were crude and strongly biased toward the collection of large particles, similar surface analyses of particles collected from high-altitude shuttle exhaust plumes are needed.