Though detailed cytological and microbiological diagnostic procedures are routinely carried out in male genital tract infection, the correct diagnosis and localization of inflammation or infection is often difficult. In this prospective study, the relevance of the seminal plasma markers PMN elastase, complement C3, CRP, fructose, PSP 94, PSA, and alpha-glucosidase was investigated in 13 patients with chronic prostatitis, 31 patients with significant leukocytospermia, and 58 patients with non-inflammatory diseases (controls). Statistically relevant results were obtained for PMN elastase when comparing chronic prostatitis with controls, leukocytospermia with controls (P < 0.001) and chronic prostatitis with leukocytospermia (P < 0.05); for complement C3 chronic prostatitis and leukocytospermia vs. controls (P < 0.05) and for fructose/ejaculate leukocytospermia vs. controls (P < 0.05). No statistically relevant differences were found for C-reactive protein, alpha-glucosidase, PSA and prostatic secretory protein (PSP 94). To delimit genital tract inflammation from non-inflammatory patients, cutpoint levels for PMN elastase of 230 ng ml-1 and for C3c of 0.01 g l-1 were suggested. PMN elastase was shown to possess the strongest discriminating power. The assessment of a cutpoint for fructose to indicate seminal vesicle dysfunction is not possible as the significance level is weak (P < 0.05).