Our aim was to compare the presence and species composition of coryneform bacteria in chronic prostatitis patients and controls. Semen of 50 men with inflammatory prostatitis and 59 controls (without pelvic pain/discomfort complaints and leukocytospermia) was investigated. First-catch urine was additionally investigated in 36 men (30 with and 6 without prostatitis). Coryneform bacteria were found in semen of 76% men with inflammatory prostatitis and 83% controls. More than half of the isolates were identified as Corynebacterium seminale. Prostatitis patients with severe leukocytospermia (>1 million white blood cells per ml) harboured significantly more Corynebacterium group G (33% vs. 2%, p = 0.0003) and Arthrobacter sp. (17% vs. 2%, p = 0.03) in comparison with controls. Nine species of coryneforms with high concentration (>or=10,000 CFU per ml) were found in prostatitis patients as against only four species in controls. Half of the men harboured corynebacteria in semen as well as in urine, 22% of men in semen only, and 3% in urine only. The total concentration of coryneforms was greater in semen than in urine (median 5000 vs. 100 CFU per ml, p = 0.053). We suggest that although coryneforms are generally considered as saprophytes, they are not uniform and some species (Corynebacterium group G and Arthrobacter sp.) may be associated with inflammatory prostatitis.