Methylglyoxal (2-oxopropanal) is a cytotoxic compound that can be formed endogenously as a by-product of glycolytic pathway; so its concentration is expected to increase when glycolysis activity increases such as during embryo development. In this work we study the effect of exogenous methylglyoxal on development and embryo viability during Bufo Bufo development and on the enzymes and cofactors involved in its detoxication process (glyoxalase I and II, reduced glutathione and glyceraldehyde 3-phosphate dehydrogenase). The results show that exogenous methylglyoxal does not affect the enzymatic pattern until stage 20, while it induces a significant activity decrease of the tested enzymes at stage 25. On the contrary methylglyoxal positively influences the reduced glutathione concentration at all the considered stages. At morphological and histological levels methylglyoxal causes a strong retardation of cell division in the early stages, that results in various abnormalities in the late development. In conclusion, methylglyoxal enters the embryo and is antiproliferative and teratogenic: the data further supports the hypothesis of the importance of the glyoxalase system in the process of cell growth and division.