A case of lymphocytic hypophysitis is described in a patient with Graves' disease and diabetes mellitus. The 62-year-old man was admitted to hospital with the complaints compatible with hyperthyroidism in April 1993. His medical history, physical examination, thyroid function tests, thyroid scintigraphy and thyroid ultrasonography revealed Graves' disease. The patient had also suffered from diabetes mellitus for three years, After this, the patient's progress was not monitored for two years. The patient presented himself again in September 1995 with complaints of hypothyroidism, hypogonadism and hypoadrenalism. Hormonal investigation showed panhypopituitarism. A magnetic resonance imaging of the pituitary gland disclosed an enlarged pituitary and a thickened infundibulum. The high intensity signal of the neurohypophysis was absent. Transsphenoidal hypophysectomy was performed which revealed a grey-white, relatively avascular pituitary mass. Histology showed diffuse infiltration of the anterior pituitary by numerous lymphocytes, The neurohypophysis also showed evidence of lymphocytic infiltration. On the basis of these findings we suggest that lymphocytic hypophysitis may be associated with Graves' disease. (C) 1998, Editrice Kurtis.