Abstract: Clonorchiasis has been prevalent in Shandong Province since 1962- Endemic areas were found to be no less than 107 counties. The village-based infection rate varies from 1 to 10% with an average of 1.6%. Most of the infested population were youngsters and children under 15 years of age. There was no marked difference in sex incidence. Cats, dogs and pigs were important reservoir hosts. Besides, rats and weasels were also found to be infected. The first intermediate hosts including Parafossarulus striatulus and Alocinma longicornis, had a wide distribution and large population. The second intermediate host is fresh water fish belonging to 23 species in 19 genera of 6 families, among which the small fishes such as Pseudorasbora parva, Abbotina revu-laris, Rhodeus atremius and Hemiculter kneri are mainly responsible for transmitting human infection. Children acquired the infection in most instances by eating underdone fish collected from ponds or ditches.