BACKGROUND Patients with esophageal achalasia are considered to be a high-risk group for esophageal carcinoma, and it has been reported that this cancer often arises at a long interval after surgery for achalasia. However, it is unclear whether esophageal carcinoma is frequent when achalasia has been treated successfully and the patient is without dysphagia. In this study, we reviewed patients with esophageal carcinoma who were detected by regular follow-up after surgical treatment of achalasia. CASE REPORT Esophageal cancer was detected by periodic upper GI endoscopy in 6 patients. Most of them had early cancers that were treated by endoscopic resection. All 6 patients had undergone surgery for achalasia and the outcome had been rated as excellent or good. Annual follow-up endoscopy was done and the average duration of follow-up until cancer was seen after surgery was 14.3 years (range: 5 to 40 years). Five patients had early cancer. Four cases had multiple lesions. CONCLUSIONS In conclusion, surgery for achalasia usually improves passage symptoms, but esophageal cancer still arises in some cases and the number of tumors occurring many years later is not negligible. Accordingly, long-term endoscopic follow-up is needed for detection of malignancy at an early stage.