The hypertensive lower oesophageal sphincter (HLOS) is a distinct clinical entity defined by a lower oesophageal sphincter (LOS) pressure > or = 30mmHg and normal LOS relaxation and oesophageal peristalsis. The clinical, physiological, and radiological details of 27 patients with HLOS diagnosed in a 3-year period were reviewed. The reasons for referral included: gastro-oesophageal reflux disease (GORD) (33%), dysphagia (18.5%), epigastric discomfort (11%), non-cardiac chest pain (15%), globus (7.5%) and other (15%). All patients had manometric evidence of HLOS (Median LOS pressure 30 mmHg, range 25-50 mmHg) and 6 patients (20.7%) had abnormal pH studies. Less than 22% of contrast studies demonstrated an abnormality. There was no change in manometric findings following pharmacological treatment. Two patients underwent oesophagomyotomy and had normal manometry on follow up. We conclude that HLOS mimics a variety of upper gastrointestinal disorders and oesophageal manometry is the gold standard of diagnosis. There was an unexpectedly high incidence of GORD (22%) in this group. The significance and treatment of HLOS is discussed.