Although transmission of hepatitis B virus (HBV) infection has long been recognised as a potential hazard of gastrointestinal endoscopy, there has been little evidence of direct patient-to-patient cross-infection after such procedures. We wish to report a case of type B viral hepatitis almost certainly acquired at endoscopy from an instrument sterilised in the conventional manner, but which had been used on the previous day on a patient with bleeding oesophageal varices who was incubating type B viral hepatitis.