Outbreak of cyanobacteria blooms, with associated unsightly scum and unpleasant odor, occurs regularly in the eutrophication lakes. Using filter-feeding fish is one of the ways to control the blooms. Based on the studies on ingestion and digestion of cyanobacteda Microcystis aeruginosa by tilapia under laboratory conditions, we carded out field testing to use tilapia to control cyanobacteria blooms in Lake Yuehu and other eutrophication lakes in Ningbo, China from 2000 to 2003. The results show that the tilapia were capable of ingesting and digesting large quantity of cyanobacteria. The average digestion rate of Microcystis aeruginosa by fingerling tilapia ranged from 58.6% to 78. 1% at the water temperature of 25℃, and the ingestion rate increased with increasing fish weight and water temperature. Outbreak of cyanobacteria blooms occurred in Lake Yuehu in both 1999 and 2000. The lake was stocked with cultured silver carp, bighead carp and mussel （9.8 g?m^-3） at the beginning of 2001 and cultured tilapia （3 - 5 g?m^-3） in April of 2002. Cyanobacteria bloom has not occurred ever since. From June to October, the average total phytoplankton density decreased from 897.6?10^6 cells? L^-1 in 2000 to 291.7?10^6 cells?L^-1 in 2001 and 183.0?10^6 cells?L^-1 in 2002. The annual average phytoplankton biomass in 2001 and 2002 decreased 48.6 % and 63.8 %, respectively, from that of 2000. The cyanobacterla as proportion of phytoplankton biomass decreased from 70% in 2000 to 22.1% in 2001 and 11.2% in 2002. In the meantime, the water transparency （Secci disk depth） increased from 20 - 50 cm to 55 - 137 cm. Similar results were obtained in some other eutrophication water bodies. For example, at the lake in Zhenghai park, algal bloom disappeared about 20 days after tilapia fingerlings were stocked （8- 15 g?m-3）. The chlorophyll a concentration and phytoplankton productivity declined dramatically whereas the water transparency increased substantially. How the stocked tilapia affects the nutrient （e. g. nitrogen and phosphorus） dynamics in the natural lakes needs further studies. Stocking tilapia is an effective measure to control cyanobacteria blooms in eutrophication water bodies, especially in lakes where the nutrient inputs cannot be reduced sufficiently, and where zooplankton cannot effectively control phytoplankton production.