Abstract: In this study, Xenopus tropicalis embryos were exposed to a known teratoen, all-trans retinoic acid (RA), for 24, 36 and 48 h. Exposure to 2, 10 and 50 μg·L-1 RA showed no effects on the survival rate of embryos, but it significantly inhibited the growth and development of embryos. RA also led to malformations in all embryos, which suggests that RA is a strong teratogen, and 〖WTBX〗X. tropicalis〖WTBZ〗 is very sensitive to RA. The most characteristic malformations were small brains, less pigmentation in eyes, pericardial edema and bent tails. After 24, 36 and 48 h of exposure, the brain teratogenic index and eye teratogenic index were significantly increased in the treatment groups, and these effects showed a good concentration-effect but not time-effect relation. The tail teratogenic index was higher in embryos after 48 h of exposure than that after 24 h of exposure. The comparisons of teratogenic phenotypes induced by RA and tributyltin indicate that RA is a good reference for revealing the mechanisms of tributyltin-mediated teratogenicity. Our results also suggest that FETAX might be modified as an assay to study the mechanisms of contaminants in future.