We are determined to extend the application range of our yeast-based tests, particularly those aimed to be used for measuring endocrine disruptive effects of environmental contaminants. We are still always improving the performance of our established tests in response to the increasing demand of efforts at the European level. For instance, proposing an environmental quality standard for priority substances, such as 17β-estradiol and 17α-ethinylestradiol, requires more efficient and rigorous biological analysis methods to enable the detection of ultralow concentrations of relevant substances. In addition to these goals, we constantly optimize all steps in the current test procedures, from sample preparation to cultivation conditions and to compositions of special test media, in order to produce reliable, sensitive bioassays and standardized test methods.