Background and objectives: Enhancer of zeste homolog 2 (EZH2) has been recently found to regulate several genes involved in immunoresponse and autocrine inflammation network. The aim of the study was to quantitate EZH2 messenger ribonucleic acid (mRNA) expression, evaluate its relation to conditions of prostatitis associated with benign prostatic hyperplasia (BPH), and correlate it with the levels of the inflammatory marker interlukin 6 (IL-6). DESIGN AND SETING: Cross-sectional study in Middle Eastern men with BPH and prostatitis or BPH only. Patients and methods: Transrectal ultrasound-guided prostate biopsies were collected from 106 patients suspected of having prostate cancer; however, the histology revealed BPH. Upon further pathological examination, 56 of these cases were identified as BPH with prostatitis and classified as: acute prostatitis (n=13); active chronic prostatitis (n=32); and, chronic inactive prostatitis (n=12). Serum IL-6 levels and EZH2 mRNA expression were measured and compared between patient groups. Results: EZH2 mRNA was overexpressed in BPH with prostatitis patients compared to BPH only patients (P<.0001). BPH with active chronic prostatitis had higher EZH2 expression than BPH with acute or chronic inactive prostatitis compared to BPH only (P=.05 and .73, respectively). EZH2 mRNA expression showed a negative correlation with IL-6 concentrations in BPH with prostatitis patients (r s=-0.31, P=.02). EZH2 overexpression was associated with an increased risk of having BPH with prostatitis (crude odds ratio 0.20, 95% CI 0.06-0.65, P=.0076). Conclusions: EZH2 mRNA expression correlates positively with prostatitis conditions associated with BPH and negatively with serum IL-6 levels. This supports the possible involvement of EZH2 mRNA overexpression in the development of prostate inflammation, and its new regulatory role in suppressing the expression of some inflammatory network genes.