A major function of transporting epithelia is vectorial ion movement. This is accomplished by ion channels, pumps, antiporters, and symporters. The activity of these transport proteins is regulated by diverse signaling transduction and membrane trafficking events, many of which involve the actin cytoskeleton. This chapter will focus on the role of actin microfilaments and associated proteins in regulation of ion transport. The apical Na+H+ antiporter NHE3 will be examined in detail in this context due to its general biological importance as well as recent advances that have helped to elucidate the mechanisms of regulation of this protein. Appreciation of the mechanisms of NHE3 regulation should serve as a framework with which to understand cytoskeletal regulation of other transport proteins as well.