In the present study, an analysis of the algae growth inhibition test was performed, which included the theoretical background of response variable selection, the statistical properties of possible response variables, the statistical analysis of test results, the reasons for differences in toxicity parameters, and the interpretation of the test results. This was done by means of a literature survey, by an analysis of a selection of 38 test reports, provided by the German Federal Environmental Agency, and by simulated tests, allowing the investigation of several test scenarios systematically.