With the protargol staining methods

the planktonic ciliated protozoans from the north region of Taihu Lake

a shallow big eutrophicated lake in China

were examinated quantitatively and qualititatively. 18 ciliate species dominated by Balanion planctonicum and Vorticella campanula were recorded. Balanion planctonicum was the first reported in China. A species of genus Askenasia identified as A. volvox previous should be A. acrostomia after observated the structures of cortex and kineties. Abundances of planktonic ciliates in the region varied from 8 400 to 32 000 ind/L with an average of 177 800 ind/L

biomass from 102 4 to 1189 6 μg/L with a mean of 359 2 μg/L In the paper the differences of results between previous reports and present research were compared and discussed.