We re-examine the GaAs(0 0 1) surface by means of first-principles calculations based on a real-space multigrid method, The c(4 x 4), (2 x 4) and (4 x 2) surface reconstructions minimize the surface energy for anion-rich, stoichiometric and cation-rich surfaces, respectively. Structural models proposed in the literature to explain the Ga-rich GaAs(0 0 1) (4 x 6) surface are dismissed on energetic grounds. The electronic proper-ties of the novel (4 x 2) structure are discussed in detail. We calculate the reflectance anisotropy of the energetically most favoured surfaces. A strong influence of the surface geometry on the optical anisotropy is found. (C) 2002 Elsevier Science B.V. All rights reserved.