Abstract The photoconductivity of KI, KBr and KCl in the fundamental absorption range was studied between —70° and 110°C. The spectral response curve consists of three characteristic regions. The first is a bell-shaped structure in the low energy tail of the intrinsic absorption band, which is temperature sensitive and presumed to be due to imperfections ; the second is a very faint photoconduction at the first exciton peak, and the third is the temperature-insensitive photoconduction above the higher energy tail of the first absorption peak due to direct photoionization in the undisturbed crystal. The direct ionization starts at ca. 5.8, 6.8 and 7.5 eV in photon energy for KI KBr and KCl, respectively.