The photochemical reaction of aqueous dichromated gelatin solution in the intrinsic sensitive region under normal room conditions as investigated employing a water-soluble gelatin. The sample solution, containing dichromate, gelatin, and pH buffer solution, was exposed, and the decrease in absorbance for the photoreduction of Cr(VI) was monitored by UV-vis spectroscopy. Having compared the behavior of gelatin with that of alcohol at photoreduction of dichromate, we found that both systems are consistent with respect to the reaction order, the kinetic order for each reactant solution. Similar results were also obtained from the standpoint of pH dependence,activation energy, and chemical sensitization by EDTA. On the basis of experimental observations and discussion, a mechanism of photoreduction of dichromated gelatin and its rate determining step were suggested.