In order to study the effect of estradiol-17beta (E2) on estrogen (E) and progesterone (P) receptors expression in oviduct and cervix of lambs, their respective transcripts (ERalpha mRNA and PR mRNA) were determined by solution hybridization and the receptor proteins (ER and PR) by binding assays after E2 treatments. Lambs (n=4 in each group) were not treated or treated with one, two or three i.m. injections of E2 (1 microg/kg) at 24 h of interval. Tissues were obtained 12 or 24 h after the last E2 injection. Estradiol treatments increased ERalpha mRNA and PR mRNA concentrations in an organ-dependent manner: transitory in the oviduct while maintained in the cervix. The E2 effect on the oviductal and cervical ER and PR concentrations were biphasic, with an initial reduction of receptors content that was followed by restoration. The ER restoration in oviduct was earlier than in the cervix. In summary, this study shows that E2 treatments may exert an inductive effect in ERalpha mRNA and PR mRNA levels and a biphasic effect in ER and PR concentrations in oviduct and cervix of immature ewe. These E2 effects varied in timing and strength depending on the organ of the reproductive tract.