For colleges with programs in London, Thursday was a day of urgent calls and e-mail messages, locating students and notifying parents that everyone was physically OK, if obviously shook up by the terrorist bombings.
Most institutions said that there were no plans to bring students home, although at least one -- Western Carolina University -- called off a planned program.
Britain is by far the top destination for American students studying abroad. In 2002-3, the last year for which complete data are available, 31,706 American students enrolled in programs in Britain, according to the Institute of International Education. (By comparison, the runner-up destination was Italy, with 18,936 students.) The data cover programs for academic credit, and study-abroad officials said that during the summer, the number of students from many American colleges in London who are just traveling may well exceed those in formal programs.
Indeed two of the hundreds of people injured Thursday were American college students who were on a vacation. The Associated Press reported that they were two sisters, one a student at the University of Tennessee and one at Pellissippi State Technical Community College. The students' injuries are not life-threatening, according to information posted on their church's Web site. 
The University of California system has nearly 350 students studying this summer in programs based in Cambridge and Sussex. Within a few hours of the bombings, all students were accounted for, and were given access to telephones to call home. Several trips planned for those students to come to London in the next week have been called off or postponed, and students have been urged to stay out of the city for the next few days.
"While we can never guarantee the safety of a student (even in California) we do all that is possible to encourage them to be careful at all times and to ensure that we know where they are and can reach them and account for them in any emergency situation," said Gayle Binion, director of California's program in Britain and a professor of political science at the University of California at Santa Barbara.
Many colleges posted information on Web sites yesterday to reassure family members of students. Michigan State University  reported that it had verified that all of its 324 students and 16 faculty members were safe, and that there was no need to call off any programs. Students were given access to a toll-free number to report on their status. Texas Christian University  posted a letter from its chancellor with the news that students were accounted for.
Syracuse University  announced that all 64 students in its London program were fine. The program has 39 students from Syracuse; the rest are from other institutions. Officials at Northwestern University started doing a headcount this morning as soon as they heard about the bombings. All 10 students in university sponsored programs are fine. The University of Notre Dame also reported that all of its students are fine.
Brigham Young University had 42 students on a program in London and by coincidence the students were on a trip that took them out of London Thursday morning, prior to the terror attacks. A Brigham Young spokesman said that the students planned to stay outside London for the next few nights.
A student from Quinnipiac University  reported that he was late this morning for his subway to his internship and just missed one of the trains that was in an explosion.
Forty-five students from Western Carolina were scheduled to depart Thursday night for a program in London, but the university called off the trip.
Many American scholars also worry about their British colleagues. Brian Leiter has been posting on his blog reports from British philosophers  about their safety.