Eighty patients were studied to determine whether dysphagia (delayed transit through oesophagus) occurs in the presence of an enlarged left atrium. Twenty-six patients (group A), with no enlargement of the left atrium but undergoing open heart surgery, were randomly selected as controls. Group B (N = 54) consisted of patients undergoing mitral valve surgery with varying degrees of left atrial enlargement. All patients were requested to swallow, in the standing position, a barium filled capsule or barium filled Slow K tablets. If there was no hold up in the oesophagus the procedure was repeated with the patient seated. When hold up occurred the patient was screened at 5, 10 and 15 min. No hold up was found in any patient in the control group (N = 26). 50% of patients with left atrial enlargement had some degree of hold up, the incidence and duration of which correlated with the size of the atrium. Hold up was just as likely to occur with a capsule or with a 'slow K' tablet. When hold up lasted for more than 15 min, water did not flush away the 'stuck' medicament, but a bolus of solid food did.