The actin cytoskeleton plays an ever-increasingly understood role in mediating a myriad of processes necessary for cellular structure and function. New and exciting information regarding the dynamic aspects of the actin cytoskeleton and its intracellular regulation are unfolding at a rapid rate. Actin cytoskeletal-surface membrane interactions mediating such diverse cellular events as cell polarity, endocytosis, exocytosis, cell division, cellular migration, cell adhesion, signal transduction, and ion channel activity are part of an ever-growing list of cellular processes dependent on precise actin polarization and regulation of assembly and disassembly. The purpose of this review is to highlight recent advances in the understanding of actin cytoskeleton-mediated cellular processes, to provide a framework that interrelates the complex protein-protein interactions necessary for localization, regulation, and mediation of these essential cellular functions, and to outline the role of actin effector proteins in the pathophysiology of ischemic cell injury.