Polycystic ovarian syndrome (PCOS) is a very common endocrine disorder in women of reproductive age. Nerve growth factor (NGF) may be involved in the pathogenesis of PCOS. In this study, we investigated the effect of Korean red ginseng extract (KRGE) on the ovarian morphology and NGF expression in an estradiol valerate (EV)-induced rat model. Polycystic ovaries were induced by a single intramuscular injection of estadiol valerate (4 mg, dissolved in sesame oil) in adult cycling rats. KRGE was administered orally (200 mg/kg body weight/day) for 60 consecutive days, beginning 60 days after the induction. Ovarian morphology was almost normalized and NGF was normalized in the EV+KRGE group. KRGE lowered the high numbers of antral follicles and increased the number of corpora lutea in the polycystic ovaries. The results are consistent with a beneficial effect of KRGE in the treatment of PCOS.