Increasing media coverage of the situation has highlighted many dramatic, individual circumstances in which foreign graduate students of high caliber have been delayed or denied entry or reentry into the U.S. to continue or complete their studies and research.

Because of concerns about the export of sensitive technologies to possibly hostile nations, foreign graduate students in the sciences seem to have been particularly affected. But very little data have accompanied the many press accounts--until recently.

Chemical & Engineering News, for one, has attempted to attach some numbers to this situation, which has drawn increasing concern in the science and engineering community at large. Over the past two months, C&EN has attempted to cull relevant data on foreign graduate students from the top U.S. graduate chemistry departments.

The picture that emerges is complex. There is a definite decline in the number of foreign graduate students who choose to study in the U.S., and their choices are more often than not driven by changes in this country's foreign student visa system.

But the declines reflect a broader reality, experts say. Even as the U.S. tightens border security, countries in Europe, Asia, and elsewhere are continuing to build their own cap