One of the most internationally used bioassays for toxicity screening of chemicals and for toxicity monitoring of effluents and contaminated waters is the acute toxicity test with "water fleas", Daphnia species. Centennial Technology initiated a new R&D project funded by Korea Ministry of Environment. The purpose of this project is to develop an automated monitor conducting 24h Daphnia acute toxicity test as well as a new method of predicting 24h EC50 values through analysing changes in the behaviour of the daphnia.