It is estimated that > 40% of new drug molecules are poorly water soluble. For many reasons, solubilisation in nonionic surfactant micelles is a favoured means of increasing apparent aqueous solubility. Recently our group has found that significant increases in drug solubilisation can be achieved by ‘matching' the hydrophobe of the surfactant with drug structure. In particular, we found that the drug, ibuprofen, is solubilised extremely well in micelles formed by the nonionic surfactant, Triton X-100, which has a hydrophobe which closely matches the structure of ibuprofen and slightly less well in micelles formed by the oliogmeric, thethered version of Triton X-100, tyloxapol. The aim of the proposed SANS study is to understand the nature of ibuprofen incorporation into Triton X-100 and tyloxapol micelles in order to aid our rational design of new, improved surfactants.