Background: Intubation failure (IF) occurs when an endoscopist is unable to progress via the oropharynx into the upper oesophagus. Aim: To assess incidence and aetiology of IF and predictors of structural pharyngeal abnormalities in patients with IF. Methods: All gastroscopies (n=26,130) performed in our centre, between August 2010 and August 2016 were retrospectively reviewed. Barium radiology and repeat gastroscopy findings were evaluated for structural causes of IF. Patients were categorised into ‘failure to tolerate’ and ‘failure to progress’ based on endoscopy reports. Results: The incidence of IF was 0.95%. Rates of IF varied with endoscopist specialty (p=0.021), but not with patient age, sex or sedation dose. Among cases of IF, structural pharyngeal abnormalities were detected on barium radiology in 28.9%, consisting of cricopharyngeal hypertrophy and/or Zenker’s diverticulum in 73.2%. ‘Failure to progress’ predicted pharyngeal pathology in 55.6%. Predictors of structural causes on barium radiology following IF included: age ≥65 (OR 4.0, 95% CI: 1.8-8.9, p<0.001); indication of dysphagia (OR 5.5, 95% CI: 2.5-11.8, p<0.001), and failure of endoscopic progression (OR 5.2, 95% CI: 2.3-12.0, p<0.001). Conclusion: Patients with IF should be investigated owing to the high risk of underlying pathology, particularly if associated with age ≥65, dysphagia, and failure of endoscopic progression. We propose that IF rates of <1% could be used as a quality indicator in gastroscopy.