Clinical, radiological, histological, and anatomical features in 2 patients with necrotizing infundibulo-hypophysitis are reported. The patients presented with a combination of diabetes insipidus and hypopituitarism. Each was found to have a sellar mass lesion with an abnormally thickened enlarged pituitary stalk that intensively enhanced on contrast magnetic resonance imaging. They were suspected to have pituitary tumors with suprasellar extension. However, tissue obtained at transphenoidal surgery revealed necrosis, fibrosis, and chronic inflammation; there was no evidence of infiltrative, infective, or neoplastic disease processes. Postoperatively, they continued to have diabetes insipidus and hypopituitarism despite radiological improvement and steroid therapy. Several clinical and anatomical features distinguish these 2 cases from classical lymphocytic hypophysitis, the most common entity in the differential diagnosis. Specifically, diabetes insipidus has not been observed preoperatively in 30 cases of lymphocytic hypophysitis, but was present in the 2 cases reported. Histological evidence of tissue necrosis present in these 2 cases is not a feature of lymphocytic hypophysitis. Pituitary stalk involvement on magnetic resonance imaging or computed tomographic scan present in these 2 cases is highly unusual in lymphocytic hypophysitis. Finally, 29 of 30 cases of lymphocytic hypophysitis were females, whereas the 2 cases reported are men. On the basis of these disparate findings, we suggest that these 2 cases represent a unique syndrome, which may be recognized clinically and radiologically.