A case of isolated vasculitis in the mammary gland of a 68-year-old female is described. Over a few months tender lumps occurred in both breasts. There were no signs of generalized disease. The sedimentation rate was normal and mammographic examination revealed no signs of malignant disease. The tumours were removed and histological examination showed inflammation, thrombosis and necrosis of medium and small arteries. We discuss the possibility of an isolated polyarteritis nodosa localized to the breast.