Objectives : Benign prostatic hyperplasia (BPH) is one of the most common diseases among elderly men. Though medicines such as 5${alpha}$-reductase inhibitor (finasteride) have recently been developed for treating BPH, their adverse effects and low efficacy should not be overlooked. Curcuma longa has a long history of use in traditional medicines of Asian countries. Many reports conclude the component curcumin in Curcuma lonfa, has the potential to treat various diseases including prostate cancer. In this study, we investigated the therapeutic effects and action mechanism of Curcuma longa with a BPH rat model. Methods : Sprague-Dawley rats were used with subcutaneous injection of testosterone after castration, which were histologically similar to human BPH. A total of 30 rats were equally divided into five groups: Group 1 served as control (sham-operated group): Group 2 was the model group: Group 3 and Group 4 animals were administered Curcuma longa at dose levels of 0.5g/kg and 1.0g/kg: Group 5 served as a positive control group and was treated with finasteride at a dose of 1 mg/kg. The drugs were administered orally once a day for 30 days consecutively. After 31 days, the prostates were removed, and analyzed for their prostatic weight and histological examination. Results : The oral Curcuma longa ingestion group showed statistically significant decreases in their prostatic weights compared with the BPH-induced group and the oral finasteride ingestion group (p<0.05). Curcuma longa is also very safe in liver and kidney up to a dose of lg/kg. Injected testosterone histologically led to prostatic hyperplasia in rats, but oral Curcuma longa ingestion decreased this change. Conclusions : These results suggest that Curcuma longa has a definite inhibitory effect on BPH and might be an alternative medicine for treatment and prevention of human BPH.