Not so long ago, people who provided DNA in the course of research studies were told that their privacy was assured. Their DNA sequences were on publicly available Web sites, yes, but they did not include names or other obvious identifiers. These were research databases, scientists said, not like the forensic DNA banks being gathered by the F.B.I. and police departments.

But geneticists nationwide have gotten a few rude awakenings, hints that research subjects in fact could sometimes be identified by their DNA alone, or even by the way their cells were using their DNA. The latest shock came in January, when a researcher at the Whitehead Institute, which is affiliated with the Massachusetts Institute of Technology, managed to track down five people selected at random from a database using only their DNA, ages and the states in which they lived. And he did it in just hours. He also found relatives — a total of close to 50 people.

This month an international group of nearly 80 researchers, patient advocates, universities and organizations like the National Institutes of Health announced that it wants to consolidate the world’s databases of DNA and other genetic information, making data easier for researchers to retrieve and share. But the security and privacy of the study subjects are paramount concerns, said Dr. David Altshuler of the Broad Institute of Harvard and M.I.T., a leader of the group.

“The problems are not yet solved in any general way,” Dr. Altshuler said. “We want to work to solve them.”