The new prostatitis classification proposes the inclusion of seminal leukocytes in the diagnosis of inflammatory chronic pelvic pain syndrome (CPPS). The present study has been performed to clarify the role of seminal leukocytes and inflammatory seminal plasma parameters in order to contribute to the differential diagnosis between inflammatory (category IIIA) and non-inflammatory (category IIIB) CPPS. A total of 112 consecutive symptomatic patients (mean age 37.3 years; range 21-64) attending our prostatitis outpatient clinic were investigated. Men with evidence for bacterial infection were excluded by prior standardized lower urinary tract localization studies. Men were categorized into inflammatory and non-inflammatory CPPS according to the leukocyte analysis in expressed prostatic secretions (EPS) and urine after prostatic massage (VB 3). Ejaculate analysis was performed after lower urinary tract localization studies. Inflammatory markers included peroxidase positive leukocytes (PPL) and PMN-elastase. Receiver operating characteristic curves were constructed to analyze cutpoints provided that the differences were significant. Increased leukocyte counts in EPS/VB 3 were found in 64 men, while in 48 this was not the case. No differences could be detected in relation to patients' age ( P>0.05). In men with category IIIA prostatitis, PPL and elastase in the seminal fluid were significantly increased ( P<0.001). For PPL and elastase, a cutpoint of 0.113 x 10(6)/ml and 280 ng/ml, respectively, were suggested. Increased PPL (>0.113 x 10(6)/ml) and elastase (>280 ng/ml) in the seminal fluid indicate inflammatory disease provided that the ejaculate analysis is performed on the same day after lower urinary tract localization studies.