The impact of stress on gastroesophageal reflux and antireflux mechanisms remains largely unexplored. To a major extent, reflux depends on a balance between gastroesophageal junction resistance to flow and gastric tone. We hypothesized that these two forces could be differently affected by stress, and to test the hypothesis we quantified in 10 healthy volunteers the effect of an acute stressful stimulus (cold pain) upon both gastroesophageal junction resistance (measured by a pneumatic resistometer) and gastric tone (measured by an electronic barostat). Such measurements were performed both under basal conditions and during stress stimulation (hand immersion in cold water for 5 min), on two separate days. The cardiovascular autonomic response was simultaneously monitored as changes in blood pressure and pulse rate. We found that, taken as a whole, cold stress significantly decreased gastroesophageal resistance (flow increase from 347 +/- 29 ml/min to 526 +/- 58 ml/min) as well as gastric tone (volume increase from 147 +/- 10 ml to 218 +/- 17 ml) (P < 0.02 for both). However, responses showed marked intra- and interindividual variation. Moreover, we found no relationship between changes in resistance to flow at the junction and either the cardiovascular autonomic response or the discomfort produced by cold stress. Changes in gastric tone were similarly unrelated to autonomic and perceptive responses. We conclude that in man experimental stress induced by cold pain tends to disrupt each of two opposite mechanisms that control gastroesophageal reflux: gastroesophageal resistance to flow and gastric tone. However, since both are decreased by stress, gastroesophageal function is largely maintained.