The efficacy and safety of Norfloxacin were studied in the treatment of 20 patients with acute epididymitis. Norfloxacin was orally administered at a dose of 200 mg 3 times a day for 14 days. Clinical efficacy rate on the 7th day was 95% (19/20), excellent in 9 cases, moderate in 10 cases and poor in 1 case, and on the 14th day was 95% (18/19), excellent in 12 cases, moderate in 9 cases and poor in 1 case. On the 14th day, fever, pain and swelling had disappeared in 8 cases (in 2 cases on the 7th day). The efficacy on the 14th day was further investigated compared to that on the 7th day. Before treatment with Norfloxacin, in 13 of the 20 patients, pyuria was observed. Cultivating the bacteria was isolated in 4 of the 13 patients. Norfloxacin remarkably affected the treatment of these patients with pyuria and bacteriuria. In the treatment with Norfloxacin, the count of leukocytes, erythrocyte sedimentation rate and CRP were obviously improved. Side effects and abnormal clinical laboratory findings were not observed. From these results, Norfloxacin 600 mg/day, t.i.d was considered useful and safe in the treatment of acute epididymitis.