In order to determine the causes of postvagotomy dysphagia, we examined microscopic changes in the lower esophagus after a proximal gastric vagotomy. Forty dogs were divided into 4 groups (n = 10). Group I was used as control. In group II, the effect of denervation was studied by means of transthoracic vagotomy. In group III, the effect of mechanical traction of the lower esophagus was studied, without denervation or surgical manoeuvres. In group IV, the effect of denervation, esophageal traction and the surgical manoeuvres, of proximal gastric vagotomy was examined. No periesophageal hematomas or fibrosis was found. Degenerative nerve phenomena were found with no significant differences in the three groups. In groups III and IV, lesions of the esophageal muscular layer were observed, without significant differences. Chronic inflammatory changes and fibrosis were also encountered being more intense and significantly more frequent in group IV. We conclude that the surgical manoeuvers necessary to obtain denervation of the cardioesophageal function during proximal gastric vagotomy, could be responsible for the appearance of post-vagotomy dysphagia.