Proposals for a financial transaction tax (FTT) have surfaced throughout the years in the United States and around the world. Recently, bills have been introduced in Congress that would tax financial transactions at rates of up to 0.5%. Similar bills have been proposed in previous Congresses. Proponents of such a tax contend that it would raise revenue while suppressing allegedly excessive trading activity. This paper examines the economic impact that an FTT would have in the U.S.