As a fundamental study on the solvent-dying, the solubility of disperse dyes in nonpolar solvents and in nonaqueous surfactant solutions was measured. The solubility of dyes nonpolar solvents was from 10-5 to 10-3 (mol/kg solvent) and was in the order of benzene>cyclohexane>n-heptane. Furthermore, a linear relation was observed between logarism of the solubility and inorganic/organic properties of dye molecules. On the other hand, the solubility of dyes in surfactant solutions was estimated in terms of the number of dye molecule dissolved by a surfactant molecule present. The solubility of an azo dye in benzene solutions of surfactants was in the order of cationic>nonionic>anionic surfactants. The solubility in anionic surfactant solutions was independent on the counter ions and bulkiness of hydrocarbon chain of surfactant molecules, but those in cationic and nonionic surfactant solutions depended on the counter ions and the ethylene oxide chain length, increasing in the order Cl-salt>Br-salt>I-salt and NP=10>NP=6>NP=4. The solubility of aminoanthraquinone dyes in anionic surfactant solutions decreased with increase of the number of amino group of dyes. The effect of solvents on the solubility of an azo dye in anionic surfactant solutions was in the order of benzene>cyclohexane>n-heptane, but it was not remarkedly affected by temperature.