Agent Orange and other herbicides were used as defoliants in the Vietnam War. Under a Congressional mandate, the Institute of Medicine (IOM) of the National Academies conducted a comprehensive review of the scientific literature to determine whether Vietnam veterans may be experiencing health effects associated with exposure to those herbicides or chemicals contaminating them. IOM's study has been updated every two years, and Veterans and Agent Orange: Update 2004 is the latest report in that series.  

As previous reports in the series have noted, there is some evidence to link certain long-term health problems with exposures to the defoliants and their various components.  For many other health outcomes, however, there is not enough epidemiologic evidence to determine whether an association exists between the condition and exposure to these chemicals.  Update 2004 reaffirms the conclusions reached in Update 2002 about specific human health effects associated with exposure to these chemicals.