The proposed existence of cholesterol-rich lipid rafts in eucaryotic plasma membranes has led to a large number of studies on the influence of cholesterol on the structure and phase behaviour of model membranes. In this article we first give a brief overview of the phase behaviour of membranes made up of binary and ternary lipid-cholesterol mixtures determined from these experiments, and then present the results of our recent x-ray diffraction and fluorescence microscopy studies on these systems. Our observations suggest a possible resolution of the reported discrepancy in the phase behaviour of these systems obtained using different experimental techniques. © 2006 Elsevier Ltd. All rights reserved.