Rho GTPases act as molecular switches to control many basic cellular activities that are also critical to the specialized functions of phagocytic leukocytes. Our laboratory has studied the regulation of Rho GTPase function, how these GTPases interact with specific effectors to modulate cell function, and how these events are coordinated in the stimulated cell. Areas of major interest include NADPH oxidase regulation by Rac2, Rac- and Cdc42-mediated control of the actin-myosin cytoskeleton via p21-activated kinase (PAK), and modulation of the apoptotic program by Rho GTPases and PAK.