Respiratory function has been associated with bone mineral density (BMD) in patients with respiratory diseases. We examined the relationship between bone density measured at the hip and respiratory function in women from the general community. A total of 4830 women aged 45-76 years were recruited from general practice age-sex registers in Cambridge between 1991 and 1995. At baseline survey, data collection included health questionnaires, measures of anthropometry, respiratory function, as well as bone mineral density BMD measured using dual energy X ray absorptiometry. BMD at total hip, femoral neck and trochanter significantly and positively correlated with FEV(1). This association was independent of age, weight, height, smoking habit, history of respiratory diseases, corticosteroids and use of hormone replacement therapy. After adjustment for these factors, an increase in FEV(1) of 1 l/s was associated with 0.026, 0.021 and 0.026g/cm(2) increase in bone mineral density at total hip, femoral neck and trochanter respectively. The association was consistent and similar in magnitude among current smokers and current non-smokers and across all age groups. The magnitude of the association was comparable to that associated with an age difference of 6 years or weight difference of 5 kg. Women in the bottom compared to top quartile of respiratory function had about double the risk of low bone density independent of other factors. Respiratory function measured using FEV(1) is positively and independently related to BMD in these middle-aged and older women across the whole normal distribution of these physiologic measures. This may reflect underlying common determinants such as physical activity. Even in healthy women, respiratory function may be a marker for women at increased risk of osteoporosis and associated fractures.