In the present study, we examined the effects of a rare earth element, lanthanum (La) on the excretion into the urine and feces as well as the distribution of calcium (45Ca) and phosphorus (32P) in the liver, pancreas, spleen, kidney, lung, heart, thymus, brain, bone and blood of male rats. The experiments were performed using 5 rats in each group. Lanthanum chloride (LaCl3) was administered orally at a dose of 100 mg/rat/d as La for 5 weeks (La-A group). 45Ca and 32P were administered orally or intravenously once, and following the administration, the urine and feces were collected daily for 8 consecutive days. As a result, the amount of oral 45Ca and 32P excreted into the feces in the La-A group increased remarkably compared with that of the control group (41→91% and 26→99%, respectively), whereas 45Ca and 32P excreted into the urine in the La-A group was reduced (9.5→0.2% and 28→0.3%, respectively). However, the excretion patterns in the urine and feces and the distribution of 45Ca and 32P in the body of rats given La, were similar to those of the control rats after the stop of the La administration (La-B group). The levels of 45Ca and 32P in the body for 8 d after their administration was highest in the control group, followed by the La-B group, and lowest in the La-A group. Moreover, in the La-A group, the levels of 45Ca and 32P in each organ decreased by 1/2 to 1/75 compared with those in the control rats, but there was no significant difference between the control group and the La-B group. However, the excretion patterns in the urine and feces and the distribution of 45Ca and 32P in the La-A group was similar to those of the control group when 45Ca and 32P were administered intravenously. These results suggest that La inhibits the uptake of 45Ca and 32P temporarily, and that the action is reversible.