To evaluate the endoscopic and histologic aspects of the esophageal mucosa in patients who underwent the Serra Dória operation for advanced megaesophagus. Thirty patients with advanced megaesophagus underwent the Serra Dória operation (operated group) and 15 patients were not submitted to surgery (non-operated group). The esophageal mucosa was evaluated by macroscopy and histologic examinations. In the operated group, 21, five and four patients with mild, moderate and severe esophagitis, respectively, were identified by endoscopy. In the non-operated group, 4 and 11 patients had moderate and severe esophagitis, respectively. The histologic examinations identified 19, six and five specimens with mild, moderate and severe esophagitis, respectively, in the operated group as opposed to one, three and 11 specimens with mild, moderate and severe esophagitis, respectively, in the non-operated group. The prevalence of severe esophagitis was high in the non-operated group while, after the Serra Dória operation, mild esophagitis was prevalent.