We assessed the relationship between dietary vitamin C intake and the level of pulmonary function (forced expiratory volume in 1 s, FEV1) in 2526 adults seen as part of the first National Health and Nutrition Examination Survey (NHANES I) between 1971 and 1974. Multiple-linear-regression analysis was performed with in FEV1 as the dependent variable. After age, height, body mass index, race, sex, cigarette smoking, and employment status were controlled for, dietary vitamin C intake was positively and significantly associated with the level of FEV1 (beta = 0.00132, P = 0.01). Interaction terms for vitamin C intake and smoking and vitamin C intake and respiratory disease were not significant. These data are consistent with the hypothesis that vitamin C intake has a protective effect on pulmonary function.