Objective To investigate the value of B7-H3 in expressed prostatic secretions (EPS) in differential diagnosis of patients with inflammatory elevation of PSA in t-PSA gray zone (4-10 ng/ml). Methods One hundred and sixteen patients from the ages of 19 to 80 years (mean, 40 years) were stu-died. In the group there were 91 chronic prostatitis (CP) patients (mean age 31 years, 19-49 years), including 11 chronic bacterial prostatitis (type II) patients, 26 inflammatory nonbacterial prostatitis (IIIA) patients and 54 noninflammatory nonbacterial prostatitis (IIIB) patients. Transrectal ultrsound guided prostate biopsy was performed on 25 patients (mean age 71 years, 62-80 years) with t-PSA in gray zone (7.21±2.60 ng/ml). Five had positive results, Gleason score was 6 in two cases, 7 in two cases and 8 in one case. Twenty patients had negative results, of whom 11 patients had inflammatory cell infiltration. EPS was collected by transrectal massage, and Enzyme-linked immunosorbent assays (ELISA) were performed for B7-H3 detection. In addition, 11 normal male controls with a mean age of 30 years (24-46 years) were recruited into the study. Volunteers were excluded if they had a history of genitourinary symptoms or surgery.Results The EPS B7-H3 levels of controls, II, IIIA, IIIB groups were 49.81±11.54, 19.33±13.90, 17.67±15.76, 25.14±13.44 ng/ml, respectively. The levels of EPS B7-H3 in positive biopsy, noninflammatory negative biopsy and inflammatory negative biopsy groups were 26.30±16.32, 30.23±18.42, 10.11±5.42 ng/ml, respectively. The highest levels were found in the control group (P<0.01). Compared to the IIIB, B7-H3 levels in II and IIIA groups were significantly lower (P<0.05). There was no significantly difference between II and IIIA groups (P>0.05). The EPS B7-H3 levels in the inflammatory negative biopsy group were statistically lower than in positive biopsy and noninflammatory biopsy groups (P<0.05). But no significant differences were found among inflammatory negative biopsy, II and IIIA groups (P>0.05). Receiver operating curve (AUC=0.883, P=0.001) utilizing EPS B7-H3 levels≤16.24 ng/ml identified patients with inflammatory elevation of PSA with a sensitivity of 78.6% and a specificity of 81.8% from patients with t-PSA in gray zone. Conclusion The EPS B7-H3 detection provides a new way for differential diagnosis of patients with inflammatory elevation of PSA in t-PSA gray zone resulting in a reduction of unnecessary prostate biopsy.