BACKGROUND: Twenty per cent of patients with heartburn do not respond to proton pump inhibitors (PPIs). Many have normal oesophageal acid exposure. We hypothesized that such PPI non-responders have heightened oesophageal sensation, and that oesophageal hypersensitivity is associated with psychiatric features including somatization and anxiety. AIM: To compare oesophageal sensation in subjects with heartburn categorized by response to PPI, and to correlate oesophageal sensation with psychiatric features. METHODS: Twenty-one PPI responders, nine PPI non-responders and 20 healthy volunteers completed questionnaires of psychiatric disorders and gastrointestinal symptoms. Subjects underwent oesophageal sensory testing with acid perfusion and balloon distension. RESULTS: Healthy volunteers displayed higher thresholds for sensation and discomfort from balloon distension than heartburn subjects (sensation P = 0.04, discomfort P = 0.14). Psychiatric disorders were associated with increased intensity of sensation (P = 0.02) and discomfort from acid (P = 0.01). Somatization was associated with increased discomfort from balloon distension (P = 0.006). Features of irritable bowel syndrome were associated with increased sensation and discomfort. CONCLUSIONS: Heartburn subjects tend to have heightened oesophageal sensation, suggesting that oesophageal hypersensitivity may persist despite therapy with PPI. Oesophageal hypersensitivity is associated with features of psychiatric disease and with the irritable bowel syndrome, which might partly explain the aetiology of heartburn symptoms that are refractory to PPI.