Off-specular neutron reflection is potentially a powerful technique for studying the lateral organisation of phospholipid bilayers. However, this has not yet been demonstrated. We have recently taken the first steps towards using this technique for studying lateral organisation with a series of preliminary experiments on mixed Langmuir monolayers as a model system. We have shown for the first time that diffuse scattering with part deuteration is sensitive to the domain organisation. In this experiment we wish to extend our preliminary monolayer studies to the more complicated bilayer case. We will fabricate a series of part deuterated mixed lipid bilayers, and by careful mainpulation of the contrasts, we will aim to separate as far as possible the contributions of fluctuations and domain organisation to the diffuse scattering from these systems.