1.1 ,This guide covers procedures for obtaining laboratory data concerning the developmental toxicity of a test material. The test utilizes embryos of the African clawed frog, Xenopus laevis and is called FETAX (Frog Embryo Teratogenesis Assay-Xenopus) (1).2 Some of these procedures will be useful for conducting developmental toxicity tests with other species of frogs although numerous modifications might be necessary. A list of alternative anurans is presented in Appendix X1.