A theoretical study is made of the temperature dependence of intrinsic and extrinsic photoconductivity in CdS-type photoconductors. The model used allows electron trapping levels and two recombination centers. Only the temperature dependence of parameters characterized by an activation energy are considered. Correlation between sub- and superlinearity and temperature dependence are studied. Some experimental results consistent with the theory are given. Non-equilibrium photoconductivity phenomena are explained in a qualitative way using the same model. Finally the effects of dark current, incompletely filled recombination centers and chemisorption on the lux-ampère characteristic are discussed.