Water solubility enhancement of phenanthrene (PHE) by a cationic Gemini surfactant (CC), four cationic and nonionic conventional surfactants (Brij35, TX 100, CPC and DTAB) as well as their equimolar binary combinations (CG/Brij35, CG/TX100, CG/CPC and CG/DTAB) have been studied and compared. Their solubilization efficiency and relationship between the structure and the solubilizing capacity towards PHE have been quantified in terms of the critical micelle concentration (CMC), the molar solubilization ratio (MSR) and the micelle-water partition coefficient (K-m). The ideality/nonideality of the mixed micelles has been discussed in light of Clint, Rubingh, Edwards and Treiner's approaches. It has been observed that both CG and equimolar binary surfactant systems remarkably enhanced the water solubility of PHE. The solubilizing capacity of CG/nonionic surfactants is particularly higher than their corresponding conventional surfactant while the contrary results have been shown by CG/cationic surfactants. This may be attributed to the "complement-counteract" effect between the micellar core solubilization and the micelle-water interface adsorption. The interaction between the Gemini and the conventional surfactants with the same chain length becomes more intense regardless of the positive or the negative effect. These results demonstrate and suggest that CG/nonionic mixed surfactants with the same chain length are more appropriate to employ for soil and water remediation. (C) 2010 Elsevier B.V. All rights reserved.