Background and Purpose: Chlorella test was performed for the first time. The interesting application of a newly proposed test in ecotoxicological research was explained. It was tested using the herbicide norflurazon as bleaching toxicant. The experimental object was green alga Chlorella kessleri Fott et Novak. [K&H, 1992]. Materials and Methods: Algae were treated on the surface of deep stock agar in tubes. Instead of dH2O t the equivalentmeasure of aqueous solution of toxicant was used in the medium. This is the essence of the Chlorella test method. Results: Already after a short period of two days, morphological changes were distinguished macroscopically. Bleaching of algae was present in particular tubes, as the result of the effect of the toxicant upon the algal growth and viability. Conclusions: We propose Chlorella test as a toxicity test that provides easy detection of sublethal, lethal and NOEC. The use of this quick, simple, indicative, cheap and applicative test is proposed as amethod for research on the preliminary effects of environmental pollutants upon green algae in culture.