We investigated the surface properties of InAs(111)A by low-temperature scanning tunneling microscopy (LT-STM) with atomic resolution and first-principles calculation. Very clear atom image was observed, showing that the surface reconstruction is an In-vacancy structure. We also observed two kinds of adsorbates on the surface. The first-principles calculations indicate that the In-vacancy structure is the most stable surface reconstruction under any experimental conditions, which is consistent with the LT-STM observation. Investigations of adsorption properties of an In atom, an As atom, and an As-2 molecule by the first-principles calculations imply that the observed adsorbates are an In atom and an As-2 molecule. (c) 2006 Elsevier B.V. All rights reserved.