The very heterogeneous, but non-random, arrangement of lipids and proteins in cell membranes are of major scientific interest and led Simons and Ikonen to propose that ¿rafts,¿ i.e. small, semi-ordered lipid domains surrounded by a disordered sea of lipid, form in cell membranes. Lipids in cell membranes are continually under attack from reactive oxygen species with the oxidation of lipids being implicated in cell apoptosis, cancer and aging. However very little work has been performed on the effect of oxidative lipid damage on lipid raft formation and the properties of rafts when partially oxidised lipids are present. We propose to use contrast variation SANS to probe the effect of the presence of oxidized lipid on the temperature and size of rafts formed. These studies will allow a better understanding of the factors leading to the formation of microdomains in biological membranes.