It was found that Thin-Layer Chromatography is useful as one of the methods to indentify the chemical structure of dye-foming developing agents. The best results were obtained on silica gel layers among various adsorbents. Diethylparamine, Droxychrome, CD-III and Agfa's dye-forming developing agent, the most popular ones, were most successfully separated when they were developed on a silica gel (WAKOGEL B-5) layer with diethylether. The method of detection described in the present work is that the developed layer is sprayed with the aqueous solution of phenol and immediately with the ammoniacal solution of silver nitrate in the light room. Dye-forming developing agents are detected as bluish colored spots, while black-and-white deveroping agents appear as dark spots. This experimental technique can be directly applied both to aqueous solutions of mineral acid salts of dye-formig developing agents and to color developers which are usually alkaline aqueous solutions.