In the Maithan dam, the Zooplanktons were represented by the Crustaceae( Cladocera, Copepoda and Ostracoda ), Rotifera& Protozoa. The Rotifera is the dominating group followed by Copepoda and then Cladocera. The invertebrates which live on, in or near the substratum of the dam water include representatives of almost every taxonomical group that occurs in fresh water. Rotifera was the abundant group representing 62% of total species, followed by Copepoda 28% and Cladocera 8%. The dominant Zooplanktons recorded in the dam were Filinia sp., Branchionus sp., Asplanchna sp. Abundance of these species indicates that the dam has become eutrophic.