Two cases of nosocomial Gram-negative bacteremia occurred following upper gastrointestinal procedures. Case1: a 55-year-old woman with esophageal cancer had undergone wire-guided intraluminal dilation of the esophageal stricture the day before the blood culture. Positive blood culture isolated Enterobacter cloacae. Case 2: a 64-year-old man with liver cirrhosis complicating esophageal varices developed laboratory-confirmed Gram-negative bacteremia twice, each episode being preceded by invasive endoscopic procedure as a treatment for esophageal varices. Positive blood culture isolated E. cloacae and Asaia lannensis, respectively. Routine antimicrobial prophylaxis is not warranted in upper GI-tract instrumentation procedures, but development of post-endoscopy nosocomial bacteremia should always be considered in immunocompromised patients. © 2013, Japanese Society for Infection Prevention and Control. All rights reserved.