Abbreviated case histories of 6 patients with brain tumor in whom mental symptoms were the first or important manifestation are presented. In these cases, the presence of a focal lesion was indicated by EEG before this was possible by initial clinical examination. [SEE SOURCE PDF FOR TABLE 1] It is recommended that, wherever possible or feasible, a routine EEG should be done on all mental hospital patients and that careful localizing electroencephalographic studies be done on all those in whom there is clinical or electroencephalographic suspicion of a focal lesion.Abstract Teaser