Transcutaneous Doppler ultrasound was used to assess the effects of exercise on both fasting and postprandial superior mesenteric artery blood flow. After treadmill exercise (speed 5 km/h, gradient 20%, duration 15 min) in 16 subjects, superior mesenteric artery blood flow decreased by 43% immediately after the end of the exercise and by 29% at five minutes and 24% at 10 minutes postexercise. The superior mesenteric artery blood flow response to a combination of a treadmill exercise and a liquid meal in 15 volunteers was significantly smaller at five minutes from the end of the stimuli, than the response to the meal alone (15 controls) (635 +/- 51 ml/min v 846 +/- 72 ml/min) (p less than 0.025), but not different at any other time. Thus exercise reduces mesenteric blood flow in both the fasting and postprandial state in normal subjects.