Paraneoplastic limbic encephalitis (PT F) is a rare disease probably caused by an immune reaction against central nervous system (CNS) structures. A 67 year old man, admitted for slurred speech, short-term loss of memory and intermittent confusions had findings compatible with limbic encephalitis and a thickened hypophysis stalk on cranial MRI. The diagnosis of limbic encephalitis was supported by cerebrospinal fluid (CSF) examination and electroencephalographic findings but anti-neuronal antibodies were negative. During the follow-up, panhypopituitarism requiring hormone replacement therapy developed and on repeated cranial MRI, new lesions were seen in the brainstem. The malignant lesion was found during gastroscopy at the gastric antrum and the histopathological diagnosis was adenocarcinoma. The patient died on the 36th day of admission.