A 57-year-old man, who had been diagnosed as having flask type, grade II achalasia of the esophagus at the age of 26, underwent Heller's esophagomyectomy in a nearby hospital in 1971. A type 0-Is lesion measuring 2 cm in size was found on the middle thoracic esophagus in September 2002. A protruding tumor with a central depression, not stained with iodine, was detected by endoscopic examination. Standard subtotal esophagectomy with three-field lymph node dissection was performed. By histopathological examination, the esophageal lesion was classified as basaloid squamous carcinoma, extending to the middle part of the submucosa (T1b; sm2), without lymph node metastasis. The majority of the invasive carcinoma was composed of basaloid carcinoma, while a part showed as squamous cell carcinoma at the mucosal site. Achalasia of the esophagus is considered as a risk factor for squamous cell carcinoma by persistent mucosal inflammation caused by chronic stasis and food retention. Most of the reported carcinomas developing from esophageal achalasia are squamous cell carcinoma histologically. An extremely rare case of superficial basaloid squamous carcinoma with achalasia is presented. © 2008 Japan Esophageal Society and Springer.