Background A prior study showed significant antibioti resistance to quinotone in our poputation.In this study we aimed to evaluate and compare the efficacy of a single versus a combined prophylactic antibiotic regimen before transrectal ultrasound-guided prostate biopsy(TRUGPB).Methods A prospective randomized study was conducted at a university hospital.Patients undergoing TRUGPB were randomized into an amoicillin-clavulanate alone(1mg;one dose before and two doses after biopsy)or an amoxicllin-clavulanate+ciprofloxacin group(250mg;one dose before and two doses after biopsy).Patients were surveyed for infection symptoms by phine on days 3 and 30 after TRUGPB.We defined an infective complication as the iccurrence of symptoms including fever,chills or rigor within 30 days after prostate biopsy,requiring medical treatment or hospitalization,aided by a tertiory-wide etectronic medical record system.Results Between November 2007 and July 2009,367 patients were randomized to either amoxicillin-clavulanate alone or amoxicillin-caavulanate+ciprofloxacin group.The infection rates after TRUGPB were 3.9％in the former group(7 out of 179 patoents)versus 0.53％(1 out of 188 patients)in the latter.Sixty-three percent(5/8)of patients with infective complications needed hospitalization.There was no intensive care unit admission or mortality during the study period.Conclusions Combining prophylactic antibiotics with amoxicllin-clavulanate+soprofloxacin significantly reduced the in cidence of infective complications after TRUGPB.We recommended a combination regimen,especially in centre with high incidence of post-TRUGPB infection.