The prospective study conducted by the Organisation internationale d'Etudes Statistiques pour les maladies de l'Oesophage (OESO) (International Organization for Statistical Studies of Esophageal Diseases) created in 1979 concerns 790 patients operated on for a tumor of the esophagus or the mouth of the esophagus. Among the preoperative investigations, endoscopic examinations were associated with a high error rate (20%). Respiratory function tests cannot constitute a formal contraindication to surgery. The value of extended surgical excision is confirmed by the results, although the need for extensive lymphatic resection has not been clearly demonstrated. The incidence of fistula has decreased, but it still remains an important element of operative deaths. However, the complications of esophagectomy are essentially pulmonary and the problem of preoperative identification of high-risk patients has not yet been resolved. The influence of various modalities of postoperative ventilation techniques were evaluated. The overall mortality rate was 14.7%, and a much broader definition of this term is required. Because of a number of contradictions in prognostic factors, the OESO group is currently testing a new clinical and histologic classification.