The solubilization of benzene, naphthalene, anthracene, and pyrene in 1-dodecanesulfonic acid micelle was measured. The maximum additive concentrations (MAC’s) of these polycyclic compounds except benzene in aqueous solution were determined spectroscopically at 25, 30, and 35 degrees C with surfactant concentration. The first stepwise association constants (K-1) between solubilizate monomer and vacant micelle were evaluated from the association equilibria between solubilizates and micelles : 1.16 x 10(3), 2.23 x 10(4), 2.53 x 10(5), and 1.09 x 10(6) mol-(1) dm(3) at 30 degrees C for benzene, naphthalene, anthracene, and pyrene, respectively. The increase in KI values with hydrophobicity of solubilizate molecules indicated that the solubilization was controlled mainly by hydrophobic interaction between the solubilizates and the micelles. Standard enthalpy and entropy changes of solubilization were calculated from the temperature change of the ($) over bar K-1 values, and the solubilization is thermodynamically discussed. Spectral microenvironments of the solubilizates in micelle were found to be much mon polar than expected from the thermodynamical parameters.