Angiotensin receptor blockers (ARBs) were developed for the treatment of high blood pressure to antagonize increased angiotensin II-dependent vasoconstriction. The aim of our study was to evaluate whether irbesartan had beneficial effects on the reduction of prostate weight in a rat model of benign prostatic hyperplasia (BPH). Benign prostatic hyperplasia was induced by subcutaneous injections of testosterone enanthate for four weeks in albino rats, and rats were treated with or without oral doses of irbesartan  (10,20 and 40mg/kg) for five consecutive days per week for four  successive weeks during BPH induction. After 4 weeks, the protein abundance of nuclear factor kappa-B was assessed immunohistochemically in the prostate tissue taken from the different treatment groups. The irbesartan (40 mg/kg)-treated group showed a significant decrease in prostate weight, prostate index and nuclear factor kappa-B abundance compared to the non-treated BPH group. These results show that irbesartan is effective in decreasing the weight and proliferation of the prostate, and suggest that irbesartan may be an effective treatment for BPH.