Lymphocytic choriomeningitis has been recognized as a distinct clinical entity for almost a half century. Wallgren1reviewed cases through 1924 and referred to this disease as "acute aseptic meningitis." In 1934 Abramson2reviewed cases up to that time. Toomey3reported seventy cases in 1936. Dummer. Lyon and Stevenson4reported twenty-two cases in 1937. There have also been reports by Gibbens,5Gordon and Abrahams,6Viets and Watts,7Ashton,8Mollaret and Kreis,9Baird and Rivers,10Rodier,11Rankin,12and Ferru.13All these reports emphasize the usual features that distinguish this entity. These are the benign course, the symptoms and signs of meningeal irritation, the spinal fluid features of pleocytosis, elevated protein content, and the absence of a bacterial agent. Only in the last five years has the virus nature of this disease been demonstrated by Armstrong and Lillie.14 Matturri-Matrai