Objective:To investigate the combined therapeutic potential of Gymnema (G.) sylvestre and Pergularia (P.) daemia on letrozole-induced polycystic ovarian syndrome (PCOS) in rats.Methods:Thirty six healthy female Wistar rats with regular estrus cycles were randomly divided into six groups each of 6. GroupⅠ received 1 mL of 0.5％ carboxyl methyl cellulose orally and served as the vehicle control group, while groupsⅡtoⅥ were treated with letrozole (1 mg/kg body weight p. o.) for 21 days to induce PCOS. After induction of PCOS, groupⅡserved as the PCOS control group, without treatment; groupⅢ received metformin (20 mg/kg body weight p. o.) as the standard group, and groups Ⅳ toⅥ received G. sylvestre (100 mg/kg body weight p. o.), P. daemia (300 mg/kg body weight p. o.), and the combination of G. sylvestre and P. daemia, respectively, for 28 days. Vaginal smears were collected from all rats daily throughout the study to determine the phases of the estrus cycle. After completing the treatment schedule, oral glucose tolerance test, serum lipid profile and reproductive hormonal analysis were carried out. Subsequently, the rats were sacrificed to collect ovary and uterus for histopathological examination. Results:The PCOS control rats showed a significant irregularity in the estrus cycle, hyperglycemia, and the altered serum lipid profile such as the increased low and very low density lipoprotein, triglyceride, and decreased high density lipoproteins. In addition, the PCOS control rats showed a significant increase in serum luteinizing hormone, testosterone, and estrogen, and decrease in follicle stimulating hormone and progesterone. These changes were significantly revoked in all the treatment groups. The test drugs also significantly reduced the gained ovary weight (P<0.001), and histopathology of the ovary showed almost normal ovary. Among the treatment groups, the group of combination treatment of G. sylvestre and P. daemia showed superior ameliorative results in PCOS parameters. Conclusions:Combination of G. sylvestre and P. daemia presents potent synergistic activity against hyperandrogenism, hyperinsulinemia, anovulation and follicular cysts in letrozole-induced PCOS rats.