Application of L3 sponge phase in preconcentration and extraction of PAH in aqua was studied. Conventional surfactant-based extraction techniques mainly utilized the hydrophobic affinity between micelles and hydrophobic extract, and phase transition of surfactant solutions for preconcentration of these hydrophobic compounds. This method is called Cloud-Point Extraction (CPT), if clouding phenomena of micellar solutions is involved in the technique. To improve the performance of surfactant-based extraction techniques, an isotropic L3 sponge phase is employed in contrast to the isotropic L1 micellar phase used in the CPT. As L3 is bicontinuous and has a better hydrophobic affinity than the L1 micellar phase, it is expected that L3 phase could result in a much higher preconcentration factor. Factors influencing the phase boundaries are investigated empirically. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).