Toxicity testing is an internationally accepted approach to ambient duality assessment. The relation between environmental chemistry and ecotoxicology is discussed. A short historical overview of ecotoxicology is described. The application potential of toxicity testing in environmental monitoring practice is assessed. The need of deeper education in ecotoxicology in connection with environmental chemistry and other sciences is mentioned. The toxicity testing is very helpful in environmental assessment programmes, but it is often incorrectly used in the Czech Republic due to lack of scientific background.