1. This study examined the influence of brisk walking on skeletal status in post-menopausal women. 2. Subjects were 84 healthy women aged 60-70 years. Who were previously sedentary and at least 5 years post-menopausal. Subjects were randomly assigned to walking (n = 43) and control (n = 41) groups. Walkers followed a 12-month, largely unsupervised programme of brisk walking. The bone mineral density of the lumbar spine, femoral neck and calcaneus and broadband ultrasonic attention of the calcaneus were measured at baseline and after 12 months. 3. Forty control subjects and 38 walkers completed the study. Walkers built up to 20.4 +/- 3.8 min/day (mean +/- SD) of brisk walking. Body mass increased in control subjects relative to walkers [mean change (SE) +0.9 (0.3) and -0.1 (0.3) kg respectively; P = 0.04]. Predicted maximum oxygen uptake increased in walkers by 2.1 (0.9) ml min-1 kg-1 (P = 0.02). Bone mineral density in the lumbar spine and calcaneus fell in control subjects [-0.005 (0.004) and -0.010 (0.004) g/cm2, respectively] but not in walkers [+0.006 (0.004) and +0.001 (0.004) g/cm2]. The difference in response between groups was significant in the calcaneus (P = 0.04) but not in the lumbar spine (P = 0.08). Mean femoral neck bone mineral density did not change significantly in either group, although changes in walkers were related to the amount of walking completed (r = 0.51, P = 0.001). The change in broadband ultrasonic attenuation of the calcaneus differed between groups [control subjects, -3.7 (0.8); walkers, -0.7 (0.8) dB/MHz; P = 0.01]. 4. Walking decreased bone loss in the calcaneus and possibly in the lumbar spine. It also improved functional capacity and enabled walkers to avoid the increase in body mass seen in control subjects.