This International Standard specifies a method for the determination of the acute toxicity to Daphnia magna Straus (Cladocera, Crustacea). This method is applicable to: — chemical substances which are soluble under the conditions of the test, or can be maintained as a stable suspension or dispersion under the conditions of the test; — industrial or sewage effluents; — treated or untreated waste water; — aqueous extracts and leachates; — fresh water (surface and ground water); — eluates of fresh water sediment; — pore water of fresh water sediment.