To study bone resorption mechanism, effect of LPS on the ⁴⁵Ca release from fetal rat ulnae and radii, and effects of carbonic anhydrase inhibitors on the LPS-induced bone resorption in organ culture were studied. Ulnae and radii were removed from 19 day old fetal rats, prelabelled by subcutaneous injection of 200^µCi ⁴⁵CaCl_² into their mother on the 17th day of gestation. Radioactivities of ⁴⁵Ca released into media were determined after 24, 48 and 72 hours. Effects of LPS and carbonic anhydrase inhibitors were observed by the ratio of % release of ⁴⁵Ca between paired control and experimental group. The observed results were as follows : 1. LPS(1^µg/ml) supplemented in media for 72hours increased the ⁴⁵Ca release significantly after 48 and 72 hours of culture and LPS(10^µg/ml) increased the ⁴⁵Ca release significantly after 72 hours of culture. 2. LPS-induced ⁴⁵Ca release was not inhibited significantly by 1mM sulfanilamide but inhibited significantly by 10mM sulfanilamide after 48 and 72 hours of culture. 3. LPS-induced ⁴⁵Ca release was not inhibited significantly by 0.1mM dichlorphenamide but inhibited signifi?cantly by 1mM dichlorphenamide after 48 and 72 hours of culture. 4. LPS-induced ⁴⁵Ca release was not inhibited significantly by 1mM acetazolamide but inhibited significantly by 5mM acetazolamide after 72 hours of culture.