This report presents evidence for urea active absorption by isolated skin of Rana esculenta. One of the supporting factors of such evidence is that at a low concentration the urea influx is five times greater than the outflux, in the absence of a chemical gradient. The transport shows a saturation kinetics with an apparent Km = 1.33 mM and is inhibited by un uncoupling agent (FCCP). 5 x 10(-4) M Phloretin, added to the external side, markedly inhibits inward urea transport, whereas it is ineffective when added to the serosal fluid. This provides evidence for a phloretin-sensitive mechanism located at the external side of the epithelium. Phloretin stimulates the sodium active transport; the possible coupling of urea and sodium movement is analysed.