About 362 million travelers (citizens and non-citizens) entered the United States in FY2013, including about 102 million air passengers and crew, 18 million sea passengers and crew, and 242 million land travelers. At the same time about 205,000 aliens were denied admission at ports of entry (POEs); and about 24,000 persons were arrested at POEs on criminal warrants. Within the Department of Homeland Security (DHS), U.S. Customs and Border Protection's (CBP) Office of Field Operations (OFO) is responsible for conducting immigration inspections at America's 329 POEs. CBP's primary immigration enforcement mission at ports of entry is to confirm that travelers are eligible to enter the United States and to exclude inadmissible aliens. Yet strict enforcement is in tension with a second core mission: to facilitate the flow of lawful travelers, who are the vast majority of persons seeking admission. A fundamental question for Congress and DHS is how to balance these competing concerns. In general, DHS and CBP rely on "risk management" to strike this balance. One part of the risk management strategy is to conduct screening at multiple points in the immigration process, beginning well before travelers arrive at U.S. POEs. DHS and other departments involved in the inspections process use a number of screening tools to distinguish between known, low-risk travelers and lesser-known, higher-risk travelers. Low-risk travelers may be eligible for expedited admissions processing, while higher-risk travelers are usually subject to more extensive secondary inspections. As part of its dual mission and in support of its broader mandate to manage the U.S. immigration system, DHS also is responsible for implementing an electronic entry-exit system at POEs. Congress required DHS' predecessor to develop an entry-exit system beginning in 1996, but the implementation of a fully automated, biometric system has proven to be an elusive goal. The current system collects and stores biographic entry data (e.g., name, date of birth, travel history) from almost all non-citizens entering the United States, but only collects biometric data (e.g., fingerprints and digital photographs) from non-citizens entering at air or seaports, and from a subset of land travelers that excludes most Mexican and Canadian visitors. With respect to exit data, the current system relies on information sharing agreements with air and sea carriers and with Canada to collect biographic data from air and sea travelers and from certain non-citizens exiting through northern border land ports; but the system does not collect data from persons exiting by southern border land ports and does not collect any biometric exit data. Questions also have been raised about DHS' ability to use existing entry-exit data to identify and apprehend visa overstayers.