It is generally understood that interactions of the integral plasma membrane proteins with the underlying cytoskeleton are responsible for many cellular processes, including cell motility, cell adhesion, cell polarity, and membrane internalization. Although a few membranecytoskeletal interactions have been defined at the molecular level, there has been no clear consensus about the overall organization of the cell cortex, a structure that includes both the membrane bilayer and its associated cytoskeleton. Views on the organization of the plasma membrane range from those in which all but a select set of plasma membrane proteins are free to diEuse in the plane of the membrane [1,2] to those in which the majority of membrane proteins are anchored in place by the cytoskeleton [ 3,4]. Furthermore, investigations of cell motility have often emphasized that the cortical actin cytoskeleton and components of the cell surface exist in a constant state of flux [ 51. Can all of these diverse views be incorporated into an overall model of the cell cortex?