Fifteen patients with primary lymphoma of breast are reported from a 30-year review. Eight of the patients were diagnosed in the last 5 years of this review, suggesting either an increase in the incidence or an increasing awareness of this condition. The age range was from 17 to 77 years. All patients presented with a breast mass and nine had histologically proven axillary node involvement. One patient had Hodgkin's disease and the remainder were non-Hodgkin's lymphoma. Treatment was by a combination of surgery, radiotherapy and chemotherapy. During follow-up which varied from 4 to 20 years (median 8 years) three patients developed metachronous involvement of the opposite breast and three died from their disease. Prognosis was related to tumour histology and stage of disease. The three who died all had high grade centroblastic lymphoma, the three largest tumours and nodal involvement. Five and ten-year survivals were 85 per cent and 73 per cent respectively, better than the survival of patients for either other non-disseminated extranodal lymphomas or breast cancer.