79 women who had been menopausal for less than 36 months and who had not received any form of treatment to prevent bone loss were randomly assigned to a 12-month regimen of calcium 500 mg/day or calcium 500 mg plus intranasal salmon calcitonin 50 IU/day for 5 days per week. After 12 months of treatment bone mineral density had decreased in the calcium-only group by a mean of 3.16 (SEM 0.6)% (p less than 0.01) but had increased in the calcium plus calcitonin group by 1.38 (0.8)% (NS). The difference in response between the two treatment groups was also highly significant (p less than 0.01), as was the difference between values for hydroxyprolinuria/creatininuria (p less than 0.01). Endogenous calcitonin levels rose significantly in the calcium group but remained unchanged in calcitonin-treated patients. Treatment by calcitonin and calcium was not followed by increased secretion of parathyroid hormone. The findings suggest that intranasal calcitonin can counteract early postmenopausal bone loss.