Immigration restrictions imposed after 11 September 2001 turned many scientists away from the United States, but complaints have now subsided and the country is striving to woo researchers back.
In this special report in this week's Nature, Geoff Brumfiel and Heidi Ledford got back in touch with scientists whose stories of immigration harassment have damaged the United States' image.
Goverdhan Mehta, a chemist, former director of the Indian Institute of Science in Bangalore, and current director of the International Council for Science, was the most high profile case.
His visa was denied because of suspicions that his work could be used to develop chemical weapons (see Top Indian science advisor refused US visa).
Mehta's visa was eventually approved, but he is undecided about accepting a renewed invitation to visit the University of Florida.
Overall, things have improved. According to US State Department statistics, the average wait for a visa had dropped from 2.5 months in 2003 to two weeks by December 2005, and the influx of foreign students has risen.
This is partly because embassies and consulates have increased their resources for handling the extended checks. US universities are also actively recruiting overseas students.