This volume gives an up-to-date account of the properties of the classes of lipids that are located in the membranes of all cells. These lipids form the essential structural components of the plasma membrane responsible for maintaining the distinct identity of the cell from its surroundings and mediating the flow of vital solutes into and out of the cell. The membrane lipids also represent reservoirs of signaling molecules that modulate a variety of physiological processes. The presentation gives a balanced perspective of what is currently known about the function of these lipids in healthy cells and tissues and what consequences follow malfunctions in their synthesis and metabolism.