Enhanced field emission on high-purity aluminum has been investigated. The current/voltage characteristic (Fowler-Nordheim plot), the chemical composition as determined by Auger electron spectroscopy and X-ray microprobe analysis, and the topography of field-emitting sites were studied locally. In addition, results on the evolution of these sites under heat treatment, Ar/sup +/ sputtering, and exposure to atmosphere are presented. The field-emitting sites on aluminum are all related to particles approximately 30 mu m in size standing on the surface. The average emission over 1-cm/sup 2/ areas is little affected by the abovementioned surface treatments.