Sportsmen and women frequently experience abdominal and chest pain during exertion. The symptoms could be cardiac but may be caused by gastro-oesophageal reflux (GOR). The aim of our study was to investigate the effect of the two activities on GOR in 17 fit, healthy adults. GOR, assessed by intraoesophageal pH, was recorded on portable monitoring equipment before, during and after rowing and running. GOR was also measured after a light meal to simulate pre-training hydration. Three studies were performed: rowing, fasted running, and post-prandial running. GOR was infrequent before exercise, being seen in only 2 subjects. However, GOR was induced in 70% of rowers, 45% of fasted runners, and 90 % of fed runners during and immediately after exercise. The presence of food in the stomach greatly increased the amount of reflux during post-prandial running, (p < 0.006 against control) but reflux was also significantly higher in those who refluxed during fasted running (p < 0.03) and rowing (p < 0.08). There was no statistical difference in the amount of GOR between the two exercise periods. This study shows that both running and rowing induce significant amounts of GOR in a normally asymptomatic group of athletes. GOR should be considered in the investigation of exertional chest pain in patients attending a sports clinic.