BACKGROUND: At least one-fourth of U.S. veterans who served in the 1990-1991 
Gulf War are affected by the chronic symptomatic illness known as Gulf War 
illness (GWI). Clear determination of the causes of GWI has been hindered by 
many factors, including limitations in how epidemiologic studies have assessed 
the impact of the complex deployment environment on veterans' health.
OBJECTIVE: We sought to address GWI etiologic questions by evaluating the 
association of symptomatic illness with characteristics of veterans' deployment.
METHODS: We compared veteran-reported wartime experiences in a population-based 
sample of 304 Gulf War veterans: 144 cases who met preestablished criteria for 
GWI and 160 controls. Veteran subgroups and confounding among deployment 
variables were considered in the analyses.
RESULTS: Deployment experiences and the prevalence of GWI differed significantly 
by veterans' location in theater. Among personnel who were in Iraq or Kuwait, 
where all battles took place, GWI was most strongly associated with using 
pyridostigmine bromide pills [odds ratio (OR) = 3.5; 95% confidence interval 
(CI): 1.7, 7.4] and being within 1 mile of an exploding SCUD missile (OR = 3.1; 
95% CI: 1.5, 6.1). For veterans who remained in support areas, GWI was 
significantly associated only with personal pesticide use, with increased 
prevalence (OR = 12.7; 95% CI: 2.6, 61.5) in the relatively small subgroup that 
wore pesticide-treated uniforms, nearly all of whom also used skin pesticides. 
Combat service was not significantly associated with GWI.
CONCLUSIONS: Findings support a role for a limited number of wartime exposures 
in the etiology of GWI, which differed in importance with the deployment milieu 
in which veterans served.