Recent papers reported that the balance between the production of IL-1ra and IL-1 probably influences the regulation of host responses, the severity and prolongation of the inflammatory reaction in some diseases. Therefore, in our continuing investigation to clarify the significance of leukocytosis and its prolongation in prostatic fluid from prostatitis patients, we investigated whether low levels of IL-1ra versus IL-1 beta secreted in prostatic fluid were the cause of prolonged prostatitis, especially nonbacterial prostatitis (NBP). As a result of the present study, we concluded that a low level of IL-1ra in relation to that of IL-1 secreted in prostatic fluid is unlikely to cause prolongation of NBP for the following reasons: (1) IL-1 beta was detected in 5 of 10 cases (50.0%), but was slightly elevated in only 2 cases (20.0%) at 14 and 17 pg/ml; (2) the average IL-1ra level was not statistically low compared with that in prostatic fluid from acute bacterial prostatitis (ABP) patients who were cured promptly with antibiotics, and (3) in 5 cases of NBP in which IL-1 beta was detected, the average IL-1ra/IL-1 beta ratio was 118 which was comparable to or even higher than that in 3 ABP and 14 acute bacterial cystitis cases in which IL-1 beta was detected and the ratios were 40 and 88, respectively.