Asthma and gastro-oesophageal reflux commonly occur together but the association in any individual may or may not be causal. Aspiration of gastric acid into the trachea has been demonstrated in some patients with asthma with concomitant falls in lung function, while acid in the lower oesophagus can exacerbate asthma by a vagal reflex following stimulation of lower oesophageal receptors. Conversely, asthma can lead to worsening reflux both through the use of smooth muscle relaxing anti-asthma medication and by the mechanical effects of hyperinflation reducing lower oesophageal sphincter pressures. The effects on asthma following treatment of reflux has been anecdotally reported to be successful in some individuals, particularly those with severe reflux, but surgery should be reserved for individuals only after failure of medical treatment and should be aimed at improving reflux symptoms rather than improving asthma control.