The adrenal gland is affected in about 25% of patients with diffuse lymphoma. Conversely, primary lymphoma is a rare cause of non-secreting adrenal tumour. We observed a recent case with exclusive right adrenal localization. An 84-year-old woman was hospitalized for asthenia, anorexia and a 3-kg weight loss. The past history included coronary heart disease. Physical examination was normal and the hemogram revealed pancytopenia. No lymphomatous infiltration was seen on the myelogram or the bone marrow biopsy. Echography of the abdomen showed a well-limited 10 cm mass above the right adrenal gland, distinct from the liver; the left gland had a normal aspect. Hormone assays were within normal limits. The right adrenal gland was removed surgically and histology revealed diffuse proliferation of medium to large sized lymphoid cells invading the entire gland. Immunohistochemistry suggested lymphoid B origin. No curative treatment was begun, but 2 months after surgery local invasion required polychemotherapy. The patient died of septic shock 5 days later. Serum cortisol measured during the septic shock eliminated adrenal gland failure. Malignant primitive non-Hodgkinien lymphomas are extremely rare and usually discovered incidentally. The tumour is always large and sometimes accompanied by adrenal insufficiency when the lesion is bilateral. In spite of suggestive imagery the diagnosis is based on the pathology examination. The lesion is usually a high-grade malignant phenotype B lymphoma. Treatment relies on chemotherapy but is disappointing.