Under the Visa Waiver Program (VWP), citizens from 27 countries can travel to the U.S. visa free. Terrorism concerns involving VWP country citizens have led some to suggest eliminating or suspending the program, while the executive branch is considering adding countries to it. Legislation passed in 2007 led the Dept. of Homeland Security to develop its Electronic System for Travel Authorization (ESTA), to screen VWP country citizens before they travel to the U.S.; if found ineligible, travelers will need to apply for a visa. This report reviewed how: (1) program elimination and suspension; (2) program expansion; and (3) ESTA could affect visa demand, resource needs, and revenues. Includes recommend. Illus.