A 21-year-old woman subacutely developed memory loss subsequent to gastroenteritis. Brain MRI with gadolinium enhancement showed symmetric involvement of the amygdala. The CSF was acellular with increased protein level. There was no evidence suggestive of neoplasm or viral infection. Combined treatment with plasmapheresis and immunoglobulin improved her clinical symptoms and lessened abnormalities manifested in the MRI. This case suggests the presence of immune-mediated limbic encephalitis without association with neoplasms or infections.