Multiple lymphomatous polyposis (MLP) is a distinctive type of primary gastrointestinal lymphoma characterized by polypoid accumulations of lymphoma tissue involving long segments of the gastrointestinal tract. A study of four cases of MLP has shown a tendency for ileocaecal involvement and extra-abdominal dissemination. The lymphoma is of centrocytic type and exhibits a nodular pattern of variable degree. Trapping of reactive follicle centres with replacement of their mantle zones is characteristic. Immunohistochemical studies show a high concentration of monotypic SIg demonstrable in both cryostat and paraffin sections together with the other features of malignant lymphoma, centrocytic. The histological features of MLP bear a close resemblance to those of intermediate cell and mantle zone lymphoma, as described by American workers, which suggests that these two conditions and malignant lymphoma, centrocytic, are the same entity. In the gastrointestinal tract malignant lymphoma, centrocytic, produces a characteristic classic clinicopathological picture (MLP). In view of its less favourable prognosis it is important to distinguish MLP from other primary gastrointestinal lymphomas of follicle centre cell origin.