The anti-osteopenic effect of nasal salmon calcitonin (SCT) was investigated in a type 1 osteoporotic model, Wistar rats which were ovariectomized (OVX) at age of 12 weeks, and compared with that of subcutaneous SCT. It was proved that nasal (5, 10, 20 and 40 U/rat) and subcutaneous (5, 10 and 20 U/kg) administration of SCT on alternate days for 3 weeks, starting a week after OVX, prevented the osteopenic changes of tibia and lumbar vertebra; this was proved by physicochemical parameters and histomorphometrically. A clear dose-dependent effect was seen in the trabecular bone volume of a selected regions of the 5th lumbar vertebra, and the ED50s of nasal and subcutaneous SCT calculated were 7.4 U/rat and 3.5 U/kg, respectively. The results indicate that nasal SCT is absorbed efficiently in rats with increased bone turnover to prevent rapidly developing osteopenia and that the administration route is a suitable standard method for chronically giving biodegradable anti-osteoporotic peptides to rats.