The photodecompositions of five typical metal dithizonates have been studied in various solvents under the irradiation of 310-nm UV light and ordinary indoor illumination. In methylene chloride and chloroform the decomposition mechanism is confirmed to be the interaction of these metal dithizonates and the oxidants arising from the photodecomposition of the solvent. In carbon tetrachloride the decompositions were fast and were observed to be first-order in the dithizonates. In benzene, no apparent photodecoraposition was found. Since these solvent effects are independent of the metal, benzene is probably the best solvent for the extraction-spectrophotometry of unstable dithizonates.