As part of the US Visit Program administered by the US Department of Homeland Security (DHS), all non-US citizens (with certain exceptions) must provide biometric information (fingerprints and photograph) upon arrival. The biometric information currently required is a scan of both index fingers and a photograph. In the near future however, a photo and scan of all 10 fingerprints will be required.
This procedure was introduced on November 29, 2007, at Washington Dulles International Airport. Other international airports across the US will follow suit during 2008.