Emphysematous prostatitis is a rare condition that is characterized by gas and abscess accumulation in the prostate. We report a 60-year-old man with emphysematous prostatitis caused by Klebsiella pneumoniae. He had a history of recently diagnosed diabetes mellitus and a 16-year history of alcoholic liver cirrhosis. He was admitted due to fever, dysuria and difficult urination. Physical examination revealed lower abdominal tenderness and prostatic fluctuance on digital examination. Leukocytosis, pyuria and elevated C-reactive protein were found. Abdominal radiography disclosed a collection of abnormal air pockets in the lower pelvic cavity and computed tomography scans corroborated the existence of extensive air collection in the prostate. Under the impression of emphysematous prostatitis, the patient was successfully treated with transurethral incision of the prostate and antibiotics for 6 weeks; there were no urinary sequelae during 6 months of follow-up. [J Formos Med Assoc 2007;106(1):74-77]