The objectives of the present study were: 1) to describe the modifications in motility of the small intestine in response to situations of psychic stress during fasting and postprandial periods. 2) To analyse the possible involvement of the vagal system in these modifications. For this we used a total of 40 dogs. The motility of the small intestine was recorded using electromyography techniques (monopolar electrodes) and manometric techniques (submucous microballons). The stress stimulus consisted in the complete body immobilization of the animal in plaster. We show that stress induced a significant increase in the intestinal motility index (percentage of show waves followed by the action potential) in the three locations of the intestine studied (duodenum, angle of Treitz and proximal part of the jejunum) during the fasting (p less than 0.001) and postprandial periods (p less than 0.001). Finally, we demonstrate that vagotomy prevents the effect of hypermotility causes by the psychic stress. We can conclude that psychic stress does indeed modify the normal motility of the small intestine, both in the fasting and postprandial periods, and the vagus is implicated in this hypermotility response.