This International Standard specifies a semi-static method for determination of toxicity of chemicals, waters and wastewaters to embryos and early larval developmental stages of a species of freshwater fish, Danio rerio (Hamilton-Buchanan), Teleostei, Cyprinidae (common name zebrafish). Where necessary this determination may include an acute toxicity test using Danio rerio to determine the 96-h LC50 for zebrafish in accordance with ISO 7346-1, ISO 7346-2 or ISO 7346-3. The method is also applicable to freshwater fish other than zebrafish if appropriate modifications of the test conditions are made, particularly with regard to the temperature and volume per fish biomass.