Aim: To investigate the value of Tc-99m ciprofloxacin imaging in the differential diagnosis of chronic bacterial prostatitis. Methods: The study included 4 normal subjects as the negative controls, 2 patients with acute prostatitis or cystourethritis as the positive controls and 59 patients diagnosed as chronic bacterial prostatitis or chronic pelvic pain syndrome by traditional laboratory tests. In every subject, the single photon emission computerized tomography images were obtained 3 h after intravenous injection of Tc-99m Ciprofloxacin. The results of the imaging were compared with those of laboratory tests. Results: On the images, negative uptake was observed in all normal subjects, while strong hot uptake, in the whole prostate of acute prostatitis patients and in the whole urethra of acute cystourethritis patients. In 13 (68 %) of 19 patients categorized as chronic bacterial prostatitis by standard laboratory tests, hot uptake with less intensity than that of acute prostatitis was observed in the Aim: To investigate the value of Tc-99m ciprofloxacin imaging in the differential diagnosis of chronic bacterial prostatitis. Methods: The study included 4 normal subjects as the negative controls, 2 patients with acute prostatitis or cystourethritis as the positive controls and 59 patients diagnosed as chronic bacterial prostatitis or chronic pelvic pain syndrome by traditional laboratory tests. In every subject, the single photon emission computerized tomography were obtained 3 h after intravenous injection of Tc-99m Ciprofloxacin. The results of the imaging were compared with those of laboratory tests. Results: On the images, negative uptake was observed in all normal subjects, while strong hot uptake, in the whole prostate of acute prostatitis patients and in the whole urethra of acute cystrethritis patients. In 13 (68%) of 19 patients categorized as chronic bacterial prostatitis by standard laboratory tests, hot uptake with less intensity than that of acute prostatitis w as observed in the