From March 1973 to September 1974, fresh-water fishes were collected in rivers in Kyungpook Province, Korea, using three collecting technics; throwing a cast-net, fishing and using a glass bowl containing crushed oil-cake as a bait.

Twenty-one species of the fish caught in the rivers in Kyungpook Province were examined for the presence of the metacercaria of Clonorchis sinensis. Of these, 10 speciec of the fish harbored the encysted larvae.

The most frequently infected one was Pseudorasbora parva 92.3 per cent, followed by Pseudogobio esocinus 90.4 per cent, Sarcocheilichthys sinensis 87.7, Hemibarbus labeo 87.2, and Pungtungia herzi 60.8 per cent, in decreasing order. The less frequently infected were Erythroculter erythropterus 13.0, Acanthorhodeus taenianalis 7.7, Paracheilognathus rhombea 5.9 and Acheilognathus limbata 4.2 per cent.

In the intensity of infection with the larvae, Pseudorasbora parva was most heavily infected and the mean number of metacercaria per ml of flesh was 51.4, Pungtungia herzi, Gnathopogon atromaculatus, Pseudogobio esocinus, Sarcocheilichthys sinensis and Homibarbus labeo were infected intermediately (Their mean number varied 10.3 to 19.5). Whereas, Paracheilognathus rhombea, Acheilognathus limbata and Acanthorbodeus taenianalis were infected with a few cysts.