Although people with diabetes have decreased lung function, the dose-response relation between measures of glucose control and lung function in nondiabetic people is not known. The authors used data from the Third National Health and Nutrition Examination Survey (1988–1994) to investigate the relation between glucose tolerance test response and other measures of glucose homeostasis and lung function in an adult population without a clinical diagnosis of diabetes. Plasma glucose level 2 hours after oral administration of 75 g of glucose was inversely related to forced expiratory volume in 1 second (FEV₁), with a difference of −144.7 ml (95% confidence interval: −231.9, −57.4) for persons in the highest quintile of postchallenge glucose compared with the lowest. Similar inverse associations with FEV₁ were found for other measures of glucose autoregulation. Lung function did not appear to be related to fasting glucose level. Similar associations were seen for forced vital capacity (FVC) but not for the FEV₁:FVC ratio. In the total study population, persons with previously diagnosed diabetes had an FEV₁ 119.1 ml (95% confidence interval: −161.5, −76.6) lower than persons without diabetes. This effect was greater in those with poorly controlled diabetes. These findings suggest that impaired glucose autoregulation is associated with impaired lung function.