Abstract: When male worms of Schistosoma japonicum were maintained at 37℃ in HBS (Hank's balanced salt solution) with ⁴⁵Ca²⁺ 1.4 mM (1.56 μCi/ml) for 30 min before addition of pyquiton, or both the drug and ⁴⁵Ca²⁺ were added to the medium simultaneously, the ⁴⁵Ca²⁺ uptake of the worms was increased significantly Within 10-30 rain. But, 30-60 rain after exposure to the drug, such increase was no longer observed. The presence of elevated Mg²⁺ (30 mM) in the incubation medium did not increase the ⁴⁵Ca²⁺ uptake of the worms The ⁴⁵Ca²⁺ uptake of male schistosomes at 4℃ was found to be increased to 18.2～51.3% in comparison with those maintained at 37℃. Meanwhile, pyquiton produced at 4℃ an apparent increase in ⁴⁵Ca²⁺ uptake of the worms. When male schistosomes that had been equilibrated with ⁴⁵Ca²⁺ were incubated in HBS without Ca²⁺ for 1-60 min, the release of ⁴⁵Ca²⁺ from the worms was more rapid than those maintained in HBS.