Surface photovoltage (SPV) spectroscopy has been used to investigate electronic surface state distributions in the forbidden band of ultrahigh vacuum (UHV) cleaved clean and gas covered (O2, H2, H2O, H2S) GaAs(110) surfaces. On cleanp‐type surfaces a correlation is found between the cleavage quality and the absolute height of the SPV for h/ω≳1.5 eV. This effect is related to surface states near midgap which are due to crystallographic defects. A similar surface state distribution is also observed after O2adsorption. Exposure to atomic hydrogen (H) causes surface states at about 0.1 eV below the conduction band or near 0.1 eV above the valence band edge. The results of H2O adsorption are interpreted in terms of empty surface states derived from a molecular H2O level; H2S adsorbs in a two‐stage process causing two different types of extrinsic surface states within the forbidden band.