Normalized neutron and X-ray reflectivity data for Langmuir monolayers composed of mixtures of dimyristoylphosphatidylcholine, DMPC and a single 18-carbon tailed sulfobetaine, SB3-18 on pure water at room temperature and at surface pressures of 15 mN/m and 35 mN/m. Neutron measurements are carried out on D2O and air contrast matched water. Measurements were carried out with deuterated and hydrogenated lipids.