The effects of hormones on production of leukaemia inhibitory factor (LIF) and the uterine receptivity in rabbits were studied. In ovariectomised rabbits, LIF protein was not detected in control but upregulated by progesterone alone. Oestrogen had a slightly negative effect when the rabbits were treated with both oestrogen and progesterone. Mifepristone (Mi) inhibited the progesterone-stimulated production of LIF in rabbit uterus. The transfer of embryos to LIF-treated recipients significantly increased pregnancy rate (70%) and implantation rate (27%) as compared with control (pregnancy rate=40% and implantation rate=17%). The transfer of embryos to LIF and mifepristone-treated recipients significantly decreased pregnancy rate (30%) and implantation rate (9%). The results indicated that LIF protein had a beneficial effect on uterine receptivity and mifepristone prevented this effect.