Abstract: This paper presents high prevalence of hydatid disease in humans and animals in Chenduo, Qinghai. By using Casoni's intradermal test (ID), indirect hemagglutination assay (IHA), and B mode ultrasonography, 820 Zans living in Chenduo were examined for hydatid disease. The positive rates assayed by the three methods were 21.0%, 11.7% and 5.0%, respectively. Forty one cases were found to harbor cystic hydatid. The infection rate was higher in females than in males, because Zang women had more chance to contact with dog and its excreta; besides, the infection rate was increasing with age. Concurrent survey of animals showed Echinococcus granulosus infection rate of 36.1% in dog, and hydatid infection rates of 52.7% and 35.0% in yak and sheep, respectively. The establishment of this parasite in dog sheep and dog yak cycles was revealed. Wild rodent Ochotona curzoniae with infection rate of 3.5% was found to be one of the intermediate hosts of E. multilocularis. Further study on E. multilocularis in domestic and/or wild animals is required.