The solubility regions of the sunscreen 2-ethyIhexyl p-methoxycinnamate (E557) in the CTAB/ n-CsHnOH/ H2O system with and without the hydrotrope agent vitamin C (VC) are determined. E357 was only sohibilized in the bicontinuous microemulsion (BI), the W/ O microemulsion area and the lamellar liquid crystal region (LLC). The addition of VC in the system greatly enlarged the solubility amount of E557in the bicontinuous region, but reduced h in the lamellar liquid crystal area. Small angle X-ray diffraction measurement was used to determine the location of E557in the lamellar liquid crystal showing the suncreen molecule penetrating between the hydrocarbon chains in the liquid crystal structure.The UV absorption spectra of E557 in various media was measured, surprisingly showing a dependence on the colloidal structure.