Brain abscess often presents unusual difficulty in diagnosis and in localization. In otitic abscess, uncertainty may arise between cerebellar and temporosphenoidal lesion. When severe infection of the ear and nose precede the general symptoms of brain abscess, without focal symptoms, confusion is likely to occur. Brain abscess develops in certain patients without any definite history of previous local infection, and localization in this group, by the usual means, frequently proves difficult or impossible. Recently I saw two patients with brain abscess of three or four months' duration that could be localized only by pneumoventriculography. REPORT OF CASES Case1.—A man, aged 44, had been sick three months when I saw him in May, 1924. His trouble began with a cold in the head. Two days later headaches were very severe, he developed pain in the right ear and the drum ruptured a few hours later. He had a severe chill,