The theory of solubility proposed by Jhon and Kihara has been tested and applied to various systems. In the present paper, the systems are the solubilities of gases such as $Ar,;H_2,;N_2,;O_2,;CO_2,;CH_4,;and;C_2H_6$ in liquid benzene and carbon disulfide, those of solids iodine and naphthalene in the nonaqueous solvents, and those of gases $H_2,;N_2,;O_2,;Ar,;CH_4,;and;C_2H_4$ in the electrolyte solutions. The theoretical values of solubilities are in good agreement with the experimental data in the literature.