The metabolism of the thyroid radioiodine was analysed by electrophoretic and chromatographic separations after 24 hrs of I¹²⁵ incorporation in two species of the genus Xenopus: Xenopus laevis laevis (Daud) and Xenopus clivii Peracca. The value of the thyroid uptake as well as its increase at metamorphic climax proved to be similar in both species. The ratio of MIT*/DIT* and T₄*/(DIT*+ MIT*) are also similar.