Abscess in the cerebellum being a rather uncommon occurrence, it is accorded in the literature less notice than abscess above the tentorium and perhaps less notice than is its due. It has its own not inconsiderable problems of diagnosis and treatment quite distinct from those of cerebral abscess, and its mortality is appreciably higher, possibly because of this lack of notice. It does not seem inappropriate, therefore, to bring forward again some of the more important considerations in its regard.To speak of otogenous cerebellar abscess is almost tautologous, since sub-tentorial abscess is almost invariably secondary to suppuration in the ear. Single metastatic abscess is so uncommon that it needs no more than mention. By chance I have had one such case which was secondary to an osteomyelitis of the tibia. 2 Infection may pass from the ear to the cerebellum by anyone of four routes-the lateral sinus, the labyrinth, the triangle of bone between the two (Trautmann's triangle), or rarely directly along the Fallopian aqueduct.