The teratogenic potential of five compounds was evaluated with FETAX (Frog Embryo Teratogenesis Assay: Xenopus). Early embryos of Xenopus laevis were exposed for 96 h to 6-aminonicotinamide (6-AN), isoniazid (INH), urethane, nitrilotriacetate (NTA) or sodium cyclamate, in two separate static-renewal tests of each compound. Based on Teratogenic Index values, growth endpoints and the types and severity of the induced malformations, 6-AN, INH and urethane scored as having strong teratogenic potential. NTA and sodium cyclamate had little or no teratogenic potential. The results support continued evaluation of FETAX as a screening assay for chemical teratogens.