The effects of a supervised 1-y walking program and increased dietary calcium (milk supplement, 831 mg/d, vs placebo drink, 41 mg/d) on bones were examined in 36 postmenopausal women (60.2 +/- 6.5 y). Trabecular bone-mineral density (BMD) of the lumbar spine (L1-L3), measured by computed tomography, increased by 0.5% in exercising women (n = 18) and decreased by 7.0% in sedentary women (n = 18; P = 0.02). Femoral-neck BMD measured by dual-photon absorptiometry (DPA) increased by 2.0% in women consuming high dietary calcium (n = 18) and decreased by 1.1% in those on moderate calcium intake (n = 18; P = 0.001). Neither exercise nor dietary calcium had an effect on lumbar spine (L2-L4) measured by DPA, distal radius measured by single-photon absorptiometry, or total body calcium measured by in vivo neutron activation. The varying proportions and rates of turnover of trabecular and cortical bone from one site to another suggest that exercise and high dietary calcium may preferentially alter bone density at different skeletal sites.