The aim of the present study was to assess the effects of continuous and cyclic salmon calcitonin (sCT) administration in the prevention of the rapid bone loss that follows ovariectomy in humans. Patients who had undergone bilateral ovariectomy 10-30 days previously received either calcium supplementation alone (500 mg/day, n = 12) or such supplementation together with nasal sCT (200 IU/day) according to a continuous (n = 20) or a cyclic (3 months on, 1 month off) regimen (n = 16) for 2 years. In the calcium-only-treated subjects urinary hydroxyproline excretion, serum alkaline phosphatase and plasma bone Gla protein levels showed a substantial increase (P < 0.01) 6 months after surgery, while radial bone density was found to have decreased significantly (P < 0.01). The patterns of biochemical markers in the sCT-treated groups indicated that nasal sCT can positively uncouple the two bone remodelling processes without inducing any significant change in radial bone density over a 2-year period. No differences were observed between the two sCT-treated groups. These results demonstrate that the rapid bone loss that follows ovariectomy can be prevented by either cyclic or continuous nasal sCT administration. Thus, cyclic nasal sCT represents an attractive alternative for the prevention of osteoporosis in postmenopausal women with contraindications to oestrogen replacement therapy.