The Rapid Androgen Disruption Activity Reporter (RADAR) Test Guideline describes an aquatic assay that utilizes transgenic Oryzias latipes (O. latipes, Japanese medaka) eleutheroembryos at day post hatch zero, in a multi-well format to detect chemicals active on the androgen axis. The RADAR assay was designed as a screening tool to provide a short-term assay to measure the response of eleutheroembryos to chemicals potentially active on the androgen axis. Test organisms are exposed for 72 hours in six-well plates in the presence and absence of a co-treatment with 17-methyl testosterone. The assay comprises five concentrations of the test chemical. At the end of the exposure, fluorescence imaging is measured and transformed into a numerical format; the statistical analysis and data interpretation procdure enable to determine whether the test chemical is considered active or not active.