alpha-galactosylceramide (a-GalCer) can activate an immune response through a protein-mediated cell signalling event. The effect of a-GalCer on local membrane structure is poorly understood but has implications for the co-localisation of the lipid and protein. Our research aims are to elucidate the effect that a-GalCer has upon the phase behaviour of model membranes and find differences between a-GalCer and naturally occurring analogues that do not elicit the same immune response. The aim of this experiment is to determine the organisation of molecules within monolayers composed of two synthetic glycolipids and their mixtures with DPPC, using neutron reflectivity. These results will be combined with our x-ray reflectivity data to yield structural information that will enable us to interpret macroscopic behaviour and so build a more complete model of a-GalCer behaviour in membranes.