N-sulfobutyl oxacarbocyanine in binary mixtures of dimethyl sulfoxide (DMSO) as a polar solvent (0.15-2 vol.%) and four less polar solvents, such as dioxane, toluene, trichloroethylene and tetrahydrofuran forms J-aggregates. Along with J-aggregates cyanine dyes form H-aggregates in the mixture of DMSO with trichloroethylene. In the mixture of DMSO with dioxane J-aggregates are formed from the monomers and the reaction proceeds with time. The relative yield of J-aggregates and the maximum rate of formation depend on the DMSO content and both are equal to zero at 5% of DMSO. J-aggregates are characterized by resonance fluorescence. For DMSO/trichloroethylene initially an H-aggregate is formed which is transformed via the monomer into a J-aggregate. The results obtained are rationalized in terms of the solvophobic effect. (C) 2010 Elsevier B.V. All rights reserved.