When a Department of Veterans Affairs panel produced a provocative report last week on the illnesses of veterans of the 1991 Persian Gulf war, it stepped into a treacherous territory where patients' suffering meets scientists' skepticism. By dismissing combat stress or other psychological causes and finding a "probable link" between the veterans' health problems and exposures to pesticides, sarin or other chemicals, the Research Advisory Committee on Gulf War Veterans' Illnesses suggested that it was correcting the record based on the latest scientific evidence. But some outside scientists, including several whose earlier gulf war studies found scant support for the...