Abstract: Freshwater crabs and snails were collected from Ninghai County in Zhejiang Province, and examined respectively for Paragonimus metacercariae and cercariae. Among 97 freshwater crabs found, the prevalence was 11.3%(11/97) with a mean intensity of 1 metacercariae per crab. It was 10.2%（5/49） and 20.2%（4/20） in the groups weighted 5-15 g and 15-25 g respectively, with an average intensity of 1, and no metacercariae were found in weight group of 25-35 g. Two positive crabs were found from 20 crabs with a low weight （< 5 g）. Male to female crabs ratio was 2.5 ∶ 1, and there was no significant difference in prevalence between males ［12.7%（7/55）］ and females ［9.1%（2/22）］. No cercariae or metacercariae were found in 200 snails （Semisulcospira libertina）.

Key words: Paragonimus, Intermediate host, Epidemiological investigation