It is commonly believed that inadverted mucosal lesions during myotomy may affect the final result of the operation. This study was therefore undertaken to determine if esophagotomy during myotomy jeopardized the outcome of the surgical treatment for achalasia. From 1992 to date, 400 laparoscopic Heller-Dor procedures were performed by 4 staff surgeons at the same institution. All patients were evaluated preoperatively by a detailed symptom questionnaire, esophageal manometry, endoscopy and barium swallow. Accidental perforation during the operation occurred in 14 patients (3.5%), that represent the object of this study (Group A). The population of the remaining 386 patients who underwent the operation uneventfully was used for comparison. Further, two different groups of patients, operated by the same surgeon immediately before (Group B) and immediately after the patients who experienced the perforation (Group C), were considered. All but 2 perforations were recognized and repaired during operation. Two perforation were detected by the routine gastrografin swallow and treated conservatively. Perforations were not related to the severity of the disease, age, duration of symptoms, LES characteristics, vigourous achalasia or surgeon's experience. A previous endoscopic treatment (87 patients) did not increase the perforation rate (2/87 vs 12/313 in the primarily treated patients, p=ns). The duration of the operation tended to be longer in Group A patients (185 min vs 135 min, p=ns); these also required a longer hospitalization (14 vs 5.5 days, p < 0.05). At a median follow up of 32 months, symptoms recurred in 2/14 (14.3%) patients who experienced a mucosal lesion, requiring complementary pneumatic dilation. That applied to 34 of the remaining 386 patients (8.8%, p=ns). Symptoms recurred in 1 patient of Group B and in none of the Group C. Further, post operative median symptom score was similar in all the 3 groups of patients. In conclusion, accidental perforation during laparoscopic Heller myotomy is infrequent and cannot be predicted by preoperative therapy or other factors such as the surgeon’s personal experience. In spite of a more complicated operation and a more prolonged recovery, the outcome of surgical treatment in these patients is similar to those undergoing uneventful myotomy. Moreover, patients undergoing the operation immediately after the same surgeon scored a mucosal perforation in a previous case, receive the same carefully performed operation and achieve the same excellent results as the patients operated before.