The present work was to observe the wormicidal effects of the external mucous substance of Carassius carassius and Pseudorasbora parva on cercaria, metacercaria (liberating) and adult of Clonorchis sinensis. The mucous substance which was extracted by ether was separated into various spots on the silica gel thin layer chromatography and separated into various fractions in the silica gel column chromatography, using petroleum ether(30 percent) and chloroform(70 percent) as solvent. R(f) 0.952 value of the silica gel thin layer chromatography and the first fraction (reddish yellow) frorn the silica gel column chromatography of the ether extracts from C. carassius had the wormicidal effect on all of the developing stages of C. sinensis. Cercaria was killed within 14 minutes, metacercaria within 27 minutes and adult 2.5 hours by the first fraction. But in the normal saline solution (control) and in the other fraction, cercaria and metacercaria were alive more than 24 hours and adult more than 72 hours. The extracts from the mucous substance of P. parva that is well penetrated by cercaria had no wormicidal effect on them.
