Narrator: This is Science Today. After the Gulf War, most American servicemen and women returned home safely. But since then, thousands have complained of symptoms ranging from memory loss to fatigue. So far, scientists have been unable to figure out what causes the so-called Gulf War Illness-or whether it even exists. Now, Dr. Michael Weiner of the University of California, San Francisco is looking to answer some of the big questions about Gulf War Illness.

Weiner: The study I'm doing is based on a previous work that was done by Robert Haley in Texas. Dr. Haley studied a group who had all been posted over to the Gulf and found that many of them had symptoms related to brain function.

Narrator: The previous study focused on a very small sample of veterans. In the new study, 400 Gulf War vets will undergo a wide battery of testing, from brain scans to memory tests.

Weiner: We'll be comparing those people who have a lot of symptoms of Gulf War Illness with those who don't have symptoms, and we'll see if Dr. Haley's findings show up or if we find something else.

Narrator: For Science Today, I'm Larissa Branin.