Résumé : The authors justify the application of the functional classifications of non-Hodgkin lymphomas to the gastrointestinal lymphomas. An illustrative case is presented. The difficulties in the histological diagnosis of these lymphomas are discussed. The role of the immunocytological and immunohistological labeling techniques is emphasized: they demonstrate the lymphoid nature of a lymphomatous growth and define accurately its cellular type. These techniques will provide a better understanding of the natural history of gastrointestinal lymphomas and of their relationship with premalignant conditions.