The efficacy of tamsulosin in the treatment of chronic non-bacterial prostatitis was evaluated in a randomized clinical observation of 105 male outpatients conducted for 90 days. Patients were randomly divided into five groups (n = 21 per group) according to prostatitis type IIIA or IIIB and therapy regimens (tamsulosin, levofloxacin, or tamsulosin plus levofloxacin combination therapy). National Institutes of Health Chronic Prostatitis Symptom Index scores, expressed prostatic massage test and urodynamic urethral pressure and urethral closure pressure tests were performed to evaluate clinical efficacy of the treatments. Scores for pain, urinary symptoms and quality of life were significantly improved by days 45 and 90 after all treatments in both prostatitis categories. Improvements in symptom scores in the combined treatment group were significantly superior to those in the single treatment groups. Tamsulosin and levofloxacin are both effective in the treatment of, and may have an additive effect in, the treatment of non-bacterial prostatitis.