We investigated the effect of clodronate on immobilization osteopenia (IO) induced by sciatic neurectomy in rats. 100 Wistar female rats were divided into 5 groups of 20 animals each: 1) sham-operated, control group, 2) IO+saline control group, 3) IO+clodronate 3 mg/kg/day, 4) IO+clodronate 10 mg/kg/day, and 5) IO+clodronate 30 mg/kg/day. Clodronate was administered subcutaneously beginning on the day after nerve sectioning. After 7 weeks, the animals were killed and both tibiae were removed. Bone mineral density, ash weight and calcium, phosphorus and magnesium contents of the ash of the tibiae were analyzed. The weight of the rats did not differ between the groups during the experiment. The ash weight of the tibiae decreased by 6.6 percent and the mineral density decreased by 5.1 percent after neurectomy. Clodronate reduced IO in a dose-dependent manner and the highest dose neutralized the effect of neurectomy. The calcium content of the ash decreased after neurectomy as compared to the sham-operated group, and clodronate increased it to the sham-operated level. The bone Ca/P ratio remained normal.