Purpose: Transurethral resection of the bladder (TURB) is a common endoscopic procedure. Perioperative antimicrobial prophylaxis (AMP) is used to reduce the risk of infectious complications. However, there is an absence of knowledge about both incidence of infectious complications after TURB and advantage of AMP in general. The objective of this study is to determinate the prevalence of postoperative infectious complications after routine TURB without AMP. Methods: We retrospectively reviewed clinical data of all patients who underwent TURB in the same Academic Urologic Department between January 2011 and December 2013. We consider as relevant for analysis, patients that underwent TURB without receiving any AMP. Infection was defined as a body temperature >37.5°C sustained for at least 24 hours. Sepsis was defined according to the third international consensus definition for sepsis and septic shock. Results: In the period of the study, 223 TURBs were performed without use of AMP. Mean age was 70.3 years (standard deviation [SD] 11.3). Mean operative time was 25.14 minutes (SD 16). Median length of hospital stay was 3 days (interquartile range [IQR]: 2-4). Six (2.7%) patients developed postoperative infective complications. No case of sepsis was reported. Two (0.9%) patients received an antimicrobial therapy with fluoroquinolones despite absence of any signs of infection. Two hundred fifteen (96.4%) patients of TURBs did not receive any antimicrobial drugs and did not develop any infectious complications. Conclusion: In our series, infectious complications after TURB occurred in