The occurrence of Sarles' phenomenon (Cerkarien Hullen Reaktion) are proved in the excysted metacercariae of Clonorchis sinensis which were incubated in the sera from rabbits given a varying number of metacercariae of C. sinensis per orally. The precipitates were formed around the oral sucker and excretory bladder of the excysted larvae. Sarles' phenomenon began to be positive from the 2nd to 3rd week after infection. In the excysted larvae of C. sinensis precipitates were not produced in the sera of rabbits infected with Metagonimus yokogawai and Capillaria hepatica. The number of eggs in the feces (E.P.G.), intradermal reaction, the course of infection and Sarles' phenomenon was studied in 6 clonorchiasis patients. Sarles' phenomenon appeared in the sera of some clonorchiasis patients. However, it assumed that this phenomenon correlated with the degree and the course of infection of clonorchiasis.
