AbstractThe Frog Embryo Teratogenesis Assay—Xenopus(FETAX) was used to assess the teratogenic potential of four solvents. Embryos of the South African clawed frog,Xenopus laevis, were exposed for 96 h to ethanol, dimethyl sulfoxide (DMSO), formamide or glycerol formal. Exposure groups were maintained using a static renewal system in which the exposure media were changed at 24‐h intervals. Survival was monitored at 24‐h intervals. Length, as an indicator of growth effects, and developmental malformations were determined at the end of the assay (96 h). Using this information, the 96‐h LC50, the 96‐h EC50(Malformation), and the no observable effect levels (NOELs) for mortality, malformation and length were determined for each solvent. The teratogenic index [TI = 96‐h LC50/96‐h EC50(Malformation)] also was calculated for each of the solvents. DMSO apeared to be the least toxic or teratogenic solvent examined, with a pooled LC50of 1.92%, a pooled EC50(Malformation) of 1.57% and TI values of 1.20 and 1.24 in replicate trials. Formamide appeared to be the most toxic solvent, with a pooled LC50of 1.04%. Data trends suggested that ethanol was the most teratogenic solvent tested, with a pooled EC50(Malformation) of 1.04% and TI values of 1.42 and 1.50. The results obtained in the present work for ethanol and DMSO were compared to previously published FETAX results for these two solvents. The present results are in close agreement with these results from other laboratories, thus providing further evidence supporting the interlaboratory reproducibility of