This report summarizes the scientific literature on 12 of the 35 pesticides that are likely to have been used during the Persian Gulf War. Where possible, it focuses on known pesticide exposures or doses and related health outcomes that may be relevant to symptoms reported by some Gulf War veterans. Evidence from studies of genetic and biological differences between ill and healthy subjects is suggestive, but not conclusive, that these pesticides could be among the potential contributing agents to some of the undiagnosed illnesses seen in Gulf War veterans. However, no prospective studies have been conducted that positively identify pesticides as causative agents. More research is needed to confirm or refute a causal link between pesticides and other agents and the symptoms associated with Gulf War illnesses.