Estrogen and progesterone use have been associated with improved pulmonary function in premenopausal women. However, little research has examined the relationship between hormone replacement therapy (HRT) and pulmonary function in postmenopausal women. We examined the relationship of HRT with spirometry in 2,353 women aged 65 yr and older participating in the Cardiovascular Health Study in 1993/1994. Current use of HRT was hypothesized to be associated with higher FEV1, higher FVC, and less pulmonary obstruction (FEV1/FVC < 65%). FEV1 was higher among current HRT users compared to noncurrent users in the following groups: overall (1.82 L versus 1.66 L, p < 0.0001), among women without asthma (1.85 L versus 1.69 L, p < 0.0001), among former smokers (1.76 L versus 1.60 L, p = 0.013), and among never smokers (1.90 L versus 1.72 L, p < 0.0001). Overall, HRT use was associated with a lower prevalence of pulmonary obstruction (OR 0.75 [95% CI 0.55, 0.99]). After controlling for potential confounders, HRT use was significantly associated with higher FEV(1) (p = 0.031) and with a lower prevalence of obstruction (OR 0.67 [95% CI 0.48, 0.95]). We conclude that postmenopausal women who use HRT have higher levels of FEV1 and less obstruction, which could not be explained by their lower rates of smoking and other health factors associated with HRT use.