Abstract: When artemether(Art)was given ig to mice on the day of infection with Schistosoma japonicum cercariae at a single dose of 300 mg.kg -1 and followed by the repeated dosing at 2-3 wk intervals,the total and female worm reduction rates as compared with the control were evident.In mice treated ig with Art on d 7 at the same dosage and repeeated once every wk for 4 times,the female worm reduction rates were about or over 90%,and part of the animals was free from female worm.Nevertheless,the liver appearance of some treated animals was similar to that of the normal mouse.The results indicated that if Art was given in the early stage after infection,it could be expected to protect the host from schistosomal infection or reduce the intensity of infection.