This International Standard specifies a method for the determination of degrees of dilution or concentrations as a measure of the acute toxic effect of waste water to fish eggs within 48 h. This International Standard is also applicable to treated municipal waste water and industrial effluents. NOTE This International Standard has been elaborated as a substitute for the acute fish toxicity test. Applied to waste water it gives the same or similar results as achieved from the acute fish toxicity test (e.g. ISO 7346 1 or ISO 7346 2). If used for single substances, possible different sensitivities from both test systems are possible.