Lymphocytic adenohypophysitis is an autoimmune disorder of the anterior pituitary gland which usually occurs in a women in the postpartum period. It has been considered that lymphocytic hypophysitis is confined to the adenohypophysis sparing the neurohypophysis, and that diabetes insipidus is not a clinical feature of the disorder. Here we report the case of a 50-year-old woman with lymphocytic hypophysitis which presented with diabetes insipidus. MRI indicated homogeneous swelling of the whole pituitary gland, loss of the normal high intensity of the posterior pituitary, and thickening of the pituitary stalk. A biopsied specimen of the pituitary revealed diffuse lymphocytic infiltration. The diabetes insipidus was controlled by the administration of DDAVP. The anterior pituitary function was not greatly damaged, and no hormonal replacement therapy was necessary. We suggest that this case represents a variant of lymphocytic adenohypophysitis and/or lymphocytic infundibuloneurohypophysitis, in which the chronic inflammatory process involves the infundibulum, adenohypophysis and neurohypophysis.