Cerebrospinal complications following antismallpox vaccination possess sufficiently characteristic pathologic features to be termed postvaccinal or cowpox encephalitis. In addition to the well known types of encephalitis, such as the epidemic (lethargic), hemorrhagic, syphilitic, and the ones complicating typhus fever, poliomyelitis and other infectious diseases, one should recognize also an encephalitis caused by cowpox. Thoroughly studied first (1912) but not published by Turnbull and McIntosh1 in England, such complications were described in 1925, in detail, by European investigators, Luksch2 in Czechoslovakia and Bastiaanse3 in Holland. The pathologic studies by Turnbull and McIntosh, Bouman and Bok,4 and especially Perdrau5 are so complete that little can be added. In general, the literature pertaining to this apparently new morbid condition and covering its various phases—clinical, epidemiologic, immunologic and bacteriologic—is extensive. It has been repeatedly referred to in the editorials, letters and abstracts of the Journal of the American Medical