The effect of therapy that simultaneously stimulates bone formation and inhibits bone resporption was evaluated in five patients with primary osteoporosis. The technique of in vivo neutron activation analysis was used to measure total body calcium (TB-Ca). The patients were treated with calcium supplements and salmon calcitonin combined with either a low or a high dose of growth hormond (hGH). There was no significant increase in skeletal mass (TB-Ca) during the low-dose hGH regimen. An increase in skeletal mass was observed in all patients following the high-dose regimen, except for one patient who developed secondary hyperparathyroidism. Although this study must be considered to be of a preliminary nature, the magnitude of the response in calcium balance suggests that skeletal mass can be increased in osteoporosis if combination therapy is employed.