Loss of height occurs with ageing. This could distort the relation between height and forced expiratory volume in 1s (FEV1) as age increases. Armspan, which approximates to height at maturity, does not fall with age and might, therefore, be a better linear variable to compare with age and spirometric volumes in older people. We studied the relation between age, height, armspan and FEV1 in 150 women aged 60-91 years. The mean value of span minus height was 4.7 cm (range -5 to +17). Standardized FEV1 (SD) in 5-year age bands between 60 and 80+ fell as follows: 1.79(0.52)1, 1.62(0.49)1, 1.38(0.41)1, 1.32(0.44)1, 1.15(0.48)1. When re-standardized using armspan, the values were: 1.76(0.48)1, 1.59(0.53)1, 1.37(0.46)1, 1.29(0.47)1, 1.11(0.54)1. The differences between the two standardized values in each age band were not significant. It was concluded that span measurements offer no advantage over height measurements in cross-sectional population studies of lung volume in old age. However, in subjects who cannot have their height measured, or who are known to have lost a substantial amount of height, armspan is a reasonable substitute measure of body size from which to calculate predicted FEV1 values.