Iron salts, e.g., FeCl3 and Fe(C1O(4))(3) promote degradation of phenol and substituted phenols if their aqueous solutions are irradiated in air, the substrate selectivity being low (i.e. the rates of degradation of different phenols an approximately equal), which is a valuable property of the proposed system from the ecological point of view. Certain solid metal oxides, e.g. CuO and V2O5, are also capable of promoting the aerobic photodegradation of phenols. However, metal oxides reveal very specific substrate selectivity. For example, CuO does not promote the degradation of unsubstituted phenol, while halogenated phenols are oxidized relatively rapidly. On the contrary, V2O5 oxidizes preferentially phenol and isomeric nitrophenols. These features reflect the difference in mechanisms operating in the cases of different oxides. Experiments with four different bioassay organisms (green algae Chlorella vulgaris, photobacteria Beneckea harveyi, infusoria Tetrahymena pyriformis and cladoceran organisms Daphnia magna) have demonstrated that oxidative photodegradation of the 2,4,5-trichlorophenol solution promoted by FeCl3, Fe(ClO4)(3) and V2O5 leads to complete or noticeable decrease in the toxicity of the solution in respect to all the organisms except Tetrahymena pyriformis. It may thus be concluded that the aerobic photodegradation of this poisonous pollutant under the action of the systems mentioned produces relatively harmless products.