Background: Published reports have documented an increased prevalence of self-reported respiratory symptoms among servicemen deployed during the 1990-1991 Gulf War. We evaluated whether this deployment resulted in long-term adverse respiratory effects. Methods: A comprehensive medical history was taken and physical and laboratory evaluations, including pulmonary function tests, were performed in 1036 deployed and 1103 nondeployed veterans of the Gulf War. Participants were classified into 5 groups on the basis of their pulmonary function tests findings: normal pulmonary function; nonreversible airway obstruction; reversible airway obstruction; restrictive lung physiology; and small airway obstruction. Results: Deployed veterans were younger, more commonly white, less educated, single, of lower mean family incomes, and more likely to have enlisted than nondeployed veterans. Deployed veterans were also statistically more likely to self-report a history of smoking and wheezing than nondeployed veterans, but comparisons of reported physician visits for pulmonary complaints, pulmonary hospitalisations, numbers of documented episodes of asthma, bronchitis, or emphysema, and pulmonary medications prescribed in the year prior to evaluation did not reveal any differences between deployed and nondeployed veterans. The distribution of pulmonary function test results was identical among deployed and nondeployed veterans. Among both deployed and nondeployed veterans, about 64% had normal pulmonary function, 16% to 18% had nonreversible airway obstruction, 10% to 12.2% had restrictive lung physiology, 6% to 6.7% had small airway obstruction, and the remaining 0.9% to 1.3% had reversible airway obstruction. Conclusion: Our findings did not confirm the hypothesis that deployment to the Gulf War in 1990-1991 resulted in an increased prevalence of clinically significant pulmonary abnormalities 10 years later.