The development of mammary glands, endocrine hormone concentrations and the gene expression of related receptors were measured in ovariectomized virgin rats after adminstration of an estrogen-like plant extract, rutin. Thirty-two ovariectomized virgin Wistar rats were randomly assigned to 4 treatments with 8 animals each: gastric infusion of 2 mL normal saline per unovariectomized rat per day (Sham), gastric infusion of 2 mL normal saline per ovariectomized rat per day (Ova), gastric infusion of 60 mg rutin kg −1 body weight (BW) per ovariectomized rat per day (Ova+Rut), or intramuscular injection of 60 μg estradiol kg −1 BW per ovariectomized rat weekly (Ova+Est). Samples of blood and mammary glands were harvested to determine the levels of estrogen (E 2 ), prolactin (PRL) and growth hormone (GH), and the gene expression of estrogen receptors (ER), prolactin receptors (PRLR) and growth hormone receptors (GHR) with radioimmunoassy (RIA) and RT-PCR technology, respectively. The E 2 concentration in plasma and gland tissues from the rats of Ovx+Rut or Ovx+Est was higher than that of Ovx (P<0.05), but the plasma E 2 concentration from the rats of Ovx+Rut was lower than that of Sham (P<0.05). The order of the PRL concentration in plasma and gland tissues was Ovx<Ovx+Rut<Ovx+Est <Sham, and the difference in each treatment (P<0.05). The plasma GH concentration was lower in Ovx than in Ovx+Rut or Ovx+Est, and lower in Ovx+Rut than in Sham (P<0.05). The GH concentration in gland tissues was lower in Ovx than in Ovx+Rut or Ovx+Est (P<0.05), and lower in Ovx+Rut than in Sham (P<0.05). The gene expression of ER in gland tissues was increased in an order as Ovx<Ovx+Rut<Ovx+Est<Sham (P<0.05), and PRLR, GHR showed the same trend. In conclusion, adminstration of rutin increased the E 2 concentration in plasma and mammary glands, promoted pituitary PRL and GH release, up-regulated the gene expression of ER, PRLR and GHR, and stimulated mammary development in ovariectomized virgin rats.