Surface reflectance spectra are observed for H-adsorbed GaAs (001) surfaces. Atomic hydrogen produced with a hot tungsten filament is adsorbed on the (2x4) surface, converting it to (1x1). Reflectance difference (anisotropy) spectra show an enhanced peak at 2.8 eV upon H adsorption at room temperature, which is not consistent with the notion that this peak originates from As dimers. Analysis of surface photoabsorption spectra show that surface dielectric changes along [(1) over bar 10] for H adsorption and for Ga deposition can be represented by a superposition of a change at the bulk critical points E(1),E(2),E(0)’ of GaAs and a broad feature centering at 2.5-2.7 eV.