['Poor pulmonary function is associated with mortality and age-related diseases, and can affect cognitive performance. However, extant longitudinal studies indicate that early cognitive ability also affects later pulmonary function. Despite the multifaceted nature of pulmonary function, most longitudinal studies were limited to a single index of pulmonary function: forced expiratory volume in 1\u2005s (FEV1). In this study, we examined whether early adult cognitive ability predicted five different indices of pulmonary function in mid-life.', 'Mixed modelling tested the association between young adult general cognitive ability (mean age=20), measured by the Armed Forces Qualification Test (AFQT), and mid-life pulmonary function (mean age=55), in 1019 men from the Vietnam Era Twin Study of Aging. Pulmonary function was indexed by per cent predicted values for forced vital capacity (FVC%p), FEV1%p, maximum forced expiratory flow (FEFmax%p), and maximal voluntary ventilation (MVV%p), and by the ratio of FEV1 to FVC (FEV1/FVC), an index of lung obstruction.', 'After adjusting for smoking, pulmonary disease, occupation, income and education, age 20 AFQT was significantly (p<0.05) associated with mid-life FVC%p (β=0.10), FEV1%p (β=0.13), FEFmax%p (β=0.13), and MVV%p (β=0.13), but was not significantly associated with FEV1/FVC (β=0.03, p=0.34).'] Do individual differences in cognitive ability at age 20 predict pulmonary function 35 years later?