BACKGROUND: α-1 blockers and dutasteride are widely used as agents to treat benign prostatic hyperplasia (BPH); the impact of these drugs on prostatic inflammation is still unclear. Herein, we investigated the impact of α-1 blockers and dutasteride treatment of BPH in terms of the degree of prostatic inflammation. MATERIALS AND METHODS: Tissue specimens were obtained from 143 BPH patients who were administered α-1 blockers up until their operation. Thirty-three of the patients had also been treated with dutasteride before the procedure. The degree of prostatic inflammation was quantified histologically by the ratio of high endothelial venule (HEV)-like vessels. We divided this retrospective cohort into α-1 blocker monotherapy and combination therapy (α-1 blockers + dutasteride) groups and evaluated clinical parameters of the two groups in relation to the degree of chronic prostatic inflammation. At the same time, we assessed factors exacerbating chronic prostatic inflammation. RESULTS: Comparison of the monotherapy and combination therapy groups showed no significant differences in the parameters of the urodynamic study or degree of chronic prostatic inflammation, whereas the IPSS total score, voiding subscore, nocturia, intermittency, weak stream, and straining were significantly lower in the combination than the monotherapy group. The duration of α-1 blockers administration was not correlated with the ratio of HEV-like vessels, while that of dutasteride was strongly correlated (correlation coefficient = 0.595; p < 0.001). Multiple regression analysis demonstrated that the duration of dutasteride administration was a key factor exacerbating the degree of chronic prostatic inflammation. CONCLUSIONS: The present study showed that despite their ameliorating effect on prostatic hyperplasia, dutasteride contributed significantly to chronic prostatic inflammation.