We investigated the incidence and characteristics of acute bacterial prostatitis after transrectal prostate biopsy, based on urine and blood cultures, treatment method, and outcome. Four hundred and fifty-seven patients who underwent transrectal prostate biopsy in our hospital between November 2003 and October 2006 were reviewed. These patients were treated with 200 mg levofloxacin orally twice daily for 4 days, beginning 12 h before biopsy, and with 200 mg isepamicin sulfate given intravenously just before the biopsy. In patients who developed acute prostatitis urine and blood cultures were checked. All organisms isolated in urine or blood cultures were tested for antibiotic susceptibility of the 457 patients, first-biopsy was performed in 371 and re-biopsy was done in 86. Acute bacterial prostatitis developed in 6 patients (1.3%). Acute prostatitis developed after a first-biopsy in 2 patients (0.5%) and after re-biopsy in 4 patients (4.7%), showing a significant difference. All of the urine and blood cultures yielded levofloxacin-resistant Escherichia coli. Immediate intravenous cephalosporin or carbapenem was effective for all of these patients. We concluded that the use of levofloxacin could be a risk factor for acute bacterial prostatitis after transrectal prostate biopsy, due to an increase in fluoroquinolone-resistant E. coli in the rectum. The incidence of prostatitis was higher in re-biopsy patients. We consider that patients should receive levofloxacin for a shorter period before biopsy to avoid generating fluoroquinolone-resistant strains. Treatment with cephalosporin or carbapenem is recommended for patients with acute prostatitis after prostate biopsy.