This proposal builds on recent work with hydrotropes alone (Langmuir, 2011, 27, 12346-12353); now co-micellisation of hydrotropes with surfactants will be investigated. The aim of this study is to explore the detailed structure of mixed hydrotrope-surfactant systems in terms of location of hydrotrope adsorbed onto, or solubilized inside, surfactant micelles. This will add important understanding to current knowledge of interactions and mechanisms involved in surfactant-hydrotrope mixtures. The results will greatly help improve the properties of industrial formulations (Agrochemical especially, as Syngenta is partly funding this project).