Single crystals of pure and Mg2+-, Ba2+-, Ca2+- and Cu2+-doped KB5 were grown by solution growth technique. The crystals were characterized by FT-IR and DRS spectral techniques. The diffuse reflectance spectra of pure and doped KB5 illustrate less absorbance for the latter than the former in the entire UV, and visible region. Photoconductivity studies carried out on pure and doped KB5 crystals revealed negative photoconductivity. Pure KB5 showed more dark and photocurrents than the doped crystals. The second energy state of Stockmann model for negative photoconductivity is suggested to have more absorption cross-section for conduction band electrons and valence band holes as the dark and photocurrents for doped KB5 crystals are less than pure KB5 crystal. (C) 2003 Elsevier B.V. All rights reserved.