Abstract: Serum samples were collected from 2 643 suspected cases of paragonimiasis in 2000-2007 from the outpatient departments of the city hospitals and surrounding areas， and the infection rate in the inhabitants， the first and second intermediate hosts， and animal reservoir hosts were investigated in the historical endemic areas. Serum samples were detected and 417 were found antibody positive （15.8%）. Among residents in the historical endemic areas，the sero-positive rate was 3.1%（46/1 462），2.8%（18/649） and 3.2% （26/813） in males and females respectively （x₂=0.183 3， P>0.05）. The infection rate in first intermediate host （snails）， second intermediate host （crabs） and animal reservoir hosts was 0.05%（9/19 368）， 31.1% （15 627/50 313） and 11.9% （52/438） respectively. Evidently， natural nidi for Paragonimus spp. still exist in Ningbo City.