Approximately 700,000 United States military personnel were deployed in the first Persian Gulf (PG) War. Several months after their return, up to 25% of Veterans had persistent symptoms which they suspected were related to their military service in the Gulf. Among the most frequent were gastrointestinal symptoms such as loose stools, excessive gas and abdominal pain. These symptoms are typical of diarrhea-predominant irritable bowel syndrome (IBS).