Achalasia, insufficient relaxation of the lower esophageal sphincter (LES) causes the retention and stasis of food and secretions, chronic hyperplastic esophagitis and eventual malignant transformation. p53 alternation has been suggested to play an important role in the malignant transformation. A 53-year-old man was endoscopically followed up for esophageal achalasia for seven years, and endoscopy revealed an ulcerative region in the upper thoracic esophagus, and histopathologically the biopsy specimens showed moderately differentiated squamous cell carcinoma. In resected specimens, p53 staining was strong and diffuse in the tumor and MIB-1 immunoreactivity was strong and patchy in the tumor and the basal layer of squamous mucosa of the esophagus. No staining for either immunostains was noted in normal esophageal mucosa. It is necessary for patients with esophageal achalasia to be followed-up with endoscopy, and that p53 and MIB-1 immunostaining of biopsy specimens should be performed to detect pre-cancerous lesions.