Chemical warfare agents were demolished by US soldiers at Khamisiyah, Iraq, in March 1991. The authors investigated postwar morbidity for Gulf War veterans, contrasting those who may have been exposed to low gaseous levels of nerve agents and those unlikely to have been exposed. Cox regression modeling was performed for hospitalizations from all causes and hospitalizations from diagnoses within 15 categories during the period March 10, 1991, through December 31, 2000, for the duration of active-duty status. After adjustment for all variables in the model, only two of 37 models suggested that personnel possibly exposed to subclinical doses of nerve agents might be at increased risk for hospitalization from circulatory diseases, specifically cardiac dysrhythmias. Of the 724 hospitalizations for cardiac dysrhythmias, 203 were in the potentially exposed group, slightly higher than expected (risk ratio = 1.23, 95% confidence interval: 1.04, 1.44). The increase was small in comparison with potential observational variability, but the findings are provocative and warrant further evaluation. Veterans possibly exposed to nerve agents released by the Khamisiyah demolition were not found to be at increased risk for hospitalizations from any other chronic diseases nearly 10 years after the Gulf War.