Gastro-oesophageal reflux disease (GOR) and asthma are both common medical conditions that often co-exist. Studies using oesophageal manometry and 24 h ambulatory pH monitoring have shown that up to 80% of asthmatics have abnormal GOR. A number of mechanisms whereby GOR may trigger asthma have been proposed, and it is believed that acid reflux may stimulate vagal receptors in the lower oesophagus causing reflex bronchoconstriction. However, GOR may be worsened by asthma causing abnormal diaphragm mechanics and by its treatment. Formal evaluation of GOR should be considered a part of asthma assessment, particularly if asthmatic symptoms are precipitated by factors known to trigger GOR such as reclining, alcohol ingestion, and the use of theophylline. Twenty-four hour ambulatory intra-oesophageal pH monitoring remains the gold standard for the diagnosis of GOR. Medical therapy with anti-reflux medications, such as acid suppressive agents and prokinetic agents may improve both GOR and asthma control. In those who fail medical therapy, anti-reflux surgery may be warranted in some.