Treatment of achalasia aims at reducing the pressure of the lower esophageal sphincter (LES) and palliate symptoms. Our objective in this study was to investigate functional changes of the esophagus after Heller myotomy and evaluate their influence on postoperative gastroesophageal reflux and esophageal morphologic changes. Between 1980 and 2003, 216 patients with achalasia underwent Heller myotomy, associated with anterior partial fundoplication (Dor fundoplication). Preoperative and long-term outcome data were collected from these patients at our hospital. The objective was to analyze esophageal functional results after Heller myotomy in the long term. Results were classified as excellent, good, fair, or poor, according to Vantrappen and Hellemans' modified classification. One-year, 2-year, 5-year, 10-year, and 20-year postoperative follow-up information was available in 100% of all patients, 91.7%, 85.1%, 60%, 52.6%, and 45.9%, respectively. There were no perioperative deaths. One year after the surgery, all patients had a significant reduction in symptoms of dysphagia and regurgitation. Five years, 10 years, 15 years, and 20 years after surgery, there were 77.2% of patients (142 in 184), 68.1%, 57.1%, and 54.5%, respectively, who were satisfied (excellent to good) with surgery. No esophageal peristalsis was demonstrated in patients during follow-up. Contractile waves in the body of the esophagus were simultaneous. The difference in the distal esophageal amplitude, the LES relaxation rate, and LES pressures in the anterior wall and/ or two sides was significant (P < 0.05) when compared before and after operation. However, there was no significant difference in the LES length and LES pressure in the posterior side. The change of direction of the LES pressure and the relaxation of LES correlate with long-term outcomes. Postoperative gastroesophageal reflux rates, including nocturnal reflux, increased with time. The percentage of patients whose esophageal diameter became normal or remained mildly increased with time in the first 10 years after surgery changed significantly. Myotomy is an effective way to palliate symptoms in patients with achalasia. Adequate myotomy can lead to reduction of LES pressure in two or three directions, which may facilitate esophageal emptying by gravity. Surgical intervention does not lead to the return of esophageal peristalsis. Functional damage of LES in patients with achalasia is irreversible.