The results of experimental studies on development a new test-model for the evaluation of toxicity, based on the application as a test-object aquatic crustaceans Cypridopsis vidua (Ostracoda), typical for ecosystems of Belarus and compares favorably with standardized test models (ease of maintenance in laboratory cultures, high reproducibility and sensitivity) are presented. The sensitivity of the test model to common environmental pollutants has been shown. The opportunity of using it to assess the acute toxicity of chemical substances and their mixtures, integral toxicity of water in Natural Bodies & Sewage. Systems, industrial waste, extracts of products has been proved. The recommendations for use in testing specific groups of substances have been proposed.