INTRODUCTION AND OBJECTIVES: Prostatic inflammation could be a key component in prostate enlargement and benign prostatic hyperplasia (BPH) progression. Our aim was to characterize inflammatory cells infiltrate within BPH tissue and to correlate inflammation and clinical data. MATERIAL AND METHODS: Inflammation was profiled on three clinical outcome tissue microarrays (TMAs), including 282 patients treated by surgery for a complicated and/or symptomatic BPH. Inflammation score was defined by combining six cytological parameters and five markers on immunohistochemistry (IHC). Cytological parameters were lymphocytes, macrophages, and polynuclears leukocytes infiltrates, and three glandular aspect modifications: glandular atrophy, glandular destruction, and tissue fibrosis. IHC markers were CD3, CD4, and CD8 decorating T-lymphocytes, CD20 decorating B-lymphocytes, and CD163 decorating macrophages. RESULTS: The majority of patients had inflammatory cells infiltrating BPH tissues: 81% had T-lymphocytes markers (CD3), 52% had B-lymphocytes markers (CD20), and 82% had macrophages markers (CD163). IPSS score (21 vs. 12; P = 0.02) and prostate volume (77 cm(3) vs. 62 cm(3); P = 0.002) were significantly higher in patients with high-grade prostatic inflammation. CONCLUSION: We characterized inflammatory cells infiltrate in a large cohort of surgically treated BPH specimens. The role of inflammation in BPH development was highlighted by the strong correlation between histological inflammation, IPSS, and prostate volume. Prostate enlargement due to chronic inflammatory process may progressively conduce to BPH progression. Therefore, inflammation is a therapeutic target for BPH.