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. Reproductive output of the parent animals and the total number of living offspring produced per parent alive at the end of the test should be reported. The study report should also include: 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, the sex ratio of the offspring may be recorded. The reproductive output of the animals exposed to the test substance is compared to that of the control in order to determine the lowest observed effect concentration (LOEC) and hence the no observed effect concentration (NOEC). In addition, and as far as possible, the data are analyzed using a regression model in order to estimate the concentration that would cause an x % reduction in reproductive output.