The test method described in this Test Guideline assesses the effect of chemicals on the reproductive output of Daphnia magna Straus. To this end, young female Daphnia are exposed to the test substance added to water at a range of concentrations (at least five). For semi-static tests, at least 10 animals at each test concentration and for flow-through tests, 40 animals divided into four groups of 10 animals at each test concentration are used. The test duration is 21 days. The total number of living offspring produced per parent animal which does not die accidentally or inadvertently during the test and the number of living offspring produced per surviving parent animal at the end of the test are reported. The study report also includes: the daily counting of the offspring, the daily recording of the parent mortality, the weekly measurement of oxygen concentration, temperature, hardness and pH values and the determination of the concentrations of test substance. Optionally other effects can be reported, including the sex ratio of the offspring. The reproductive output of the animals exposed to the test substance is analysed, by comparing it with that of the control in order to determine the lowest observed effect concentration (LOEC) and hence the no observed effect concentration (NOEC), and by estimating the concentration that causes an x % reduction in reproductive output by means of a regression analysis.