Photolysis of an azo, a quinophthalone, and several anthraquinone smoke dyes was studied on soil surfaces. Initially, rapid photodegradation of each dye occurred, followed by a period of much slower rate of loss, indicating that the remaining fraction of the dye was photochemically protected. The average mean depths of photolysis ranged from 0.33 to 0.68 mm for outdoor studies and from 0.42 to 0.73 for lab studies. The magnitude of the mean depth of photolysis suggests that photo-degradation of the dyes occurs through indirect photochemical processes. Photolysis products for only two of the dyes could be identified. Photolysis of Disperse Red 9 resulted in the formation of 1-aminoantraquinone, whereas Solvent Yellow 33 photodegraded to give 2-carboxyquinoline and phthalic anhydride. Reaction mechanisms involving sensitized photo-oxidation by singlet oxygen are consistent with the formation of these reaction products.