During gastrointestinal endoscopy, endoscopes are exposed to millions of bacteria that constitute the gut flora. Unlike “critical” devices (such as laparoscopes), which require sterilization because they breach sterile tissue planes, endoscopes are still categorized as “semicritical” devices according to the Spaulding classification. Flexible endoscopes are not suitable for steam sterilization. The reprocessing procedure is based on detergent cleaning and high-level disinfection. Inadequate flexible endoscope reprocessing has been associated with infection outbreaks, most recently caused by carbapenem-resistant Enterobacteriaceae. Lapses in essential device reprocessing steps such as cleaning, disinfection/sterilization, and storage have been reported, but some outbreaks have occurred despite claimed adherence to established guidelines.