The parkinsonian syndrome following epidemic encephalitis has terminated fatally with sufficient frequency to permit numerous, though scattered, observations on the pathologic picture. The following brief review of the available literature will serve to indicate the differences of opinion which exist, relative particularly to the rôle of the globus pallidus or substantia nigra lesions in the production of the syndrome. Lesions in the substantia nigra have been admitted by proponents of the idea that globus pallidus involvement is the essential feature of the pathogenesis of the disease and, conversely, globus pallidus lesions have been described by most of the observers who would place the seat of the difficulty in the substantia nigra. Up to the present no one has undertaken a detailed evaluation of the quantitative amount of cell destruction in these regions in any case. The purpose of this paper is to present the findings of such a study in