The classical bilayer model of cell membrane structure proposed by Singer and Nicholson in 1972 has recently been modified. Research has shown that lipid molecules in the membrane do not have a random horizontal distribution but form submicroscopic domain enriched in cholesterol, sphin- golipids and gangliosides. These lipid microdomain (also named lipid rafts) have been visualised in living cells by a variety of methods including fluorescence microscopy with lipid-specific probes, scanning probe microscopy and cryoelectron microscopy. Rafts can be purified by ultracentrification and flotation techniques. Lipid rafts play a key functional role in cell metabolism by means of their associa- tion with a variety of important membrane molecules, including cytokine and growth factor receptors, death receptors or non-receptor protein kinases. In this paper we briefly review the role of lipid rafts in cell homeostasis and their pathogenic significance in infection diseases, cancer, chronic inflammation, diabetes and degenerative disorders of the central nervous system.