The component communities of intestinal helminths in carp, Cyprinus carpio, were investigated in six lakes in the highland of Yunnan province of southwest China. The species compositions of the communities were poor, and the degree of similarity was low between the communities. The helminth species richness of the communities was related to the lake area. The island theory may provide a good explanation for the species compositions of the helminth communities, although the fauna composition of the lakes may be the major determinant of the species compositions. However, introduction and colonization may have also played a role in determining the species richness at lease in some of the six lakes, for example in Lugu lake where C. carpio, an introduced fish was infected with Bothriocephalus sp. As these lakes are ecologically and geographically isolated and some species of fish are lake-specific, it is suggested that host-parasite coevolution may also be important in determining the parasite species compositions.