This study was undertaken to examine the effect of estrogen replacement therapy alone and estrogen replacement therapy plus variable-resistance weight training on the bone mineral content of surgically menopausal women. A total of 20 surgically menopausal women were randomized and treated with either 0.625 mg conjugated estrogen daily or the same dose of estrogen plus a closely monitored exercise program involving the use of Nautilus muscle strengthening/endurance equipment. After 1 year's observation, the bone mineral density (BMD) of the spine determined by dual-photon absorptiometry increased in the exercising subjects by 8.3 +/- 5.3% (p = 0.004), 95% confidence limits (CL) 3.9-12.8%; the group with estrogen replacement therapy alone maintained their BMD: 1.5 +/- 12.4% (p = 0.36; 95% CL = -6.9-9.8%). The total body BMD of the exercising group increased by 2.1 +/- 1.5% (p = 0.003; 95% CL = 0.8-3.3%); the nonexercising women had a nonsignificant 0.6 +/- 2.9% change (p = 0.30; 95% CL = -1.4-2.5%). A significant increase of 4.1 +/- 4.3% (p = 0.01; 95% CL = 0.8-7.4%) in the radial midshaft BMD of the exercising group was found; the estrogen alone group recorded a nonsignificant change of -0.3 +/- 3.1% (p = 0.33; 95% CL = -1.7-2.4%). The results of this study suggest that variable-resistance training in estrogen-replete women adds bone to both the axial and appendicular skeleton.