We studied the influence of inorganic salts and bases on absorption and fluorescence spectra of diluted aqueous solutions of 5, 6-dichloro-2-[3-[5, 6-dichloro-l-ethyl-3-(3-sylfopropyl)-2(3H)-benzimidazolidene]-1-propenyl]-1-ethyl-3-(3-sulfopropyl) benzimidazolium hydroxide, inner salt, sodium salt (TDBC). Addition of inorganic salts or bases led to the appearance of an intense J-band and to the disappearance of monomer bands, even when the concentration of TDBC was as small as 2.3 x 10(-8) mol/L. Salts and bases also significantly changed the maximal temperature at which the J-band was still observed in the spectra of the solutions. Finally, they affected the position of the maximum and the shape of the J-band.