Intracranial tumors are of fairly common occurrence, but it would be impossible to state their exact incidence. Many cases are not recognized during life, the tumor being discovered at the post-mortem examination. Undoubtedly many more cases remain unrecognized in patients for whom a necropsy is not done or only a necropsy which does not include opening the head. Some idea can be gained, however, from the following statistics:According to the Census Bureau report of mortality in the United States Registration Area for 1930, all deaths (exclusive of stillbirths), deaths from cancers and other tumors, and deaths from brain tumors were distributed in the white population, by sex and age groups, as given in Table XLVIII. 1 -The census figures show that 99.07 per 1000 of all deaths were deaths from various tumors; and 0.68 per 1000 of all deaths were deaths from brain tumors. The figures also show that the factors of age and sex have an important influence on mortality from tumors in general and from brain tumors.-For tumors in general the highest figure per 1000 of all deaths is found in the age group of 40 to 59 years, namely, 154.94. For brain tumors the figures are lowest in the age groups under 5 years, and 60 years or more: 0.06 and 0.22, respectively; but are relatively highest and vary little in the age groups of 5 to 59 years, the average for these groups being 1.48.-Tumors in general are, on the whole, distinctly more common in the female sex; but brain tumors are slightly more common in the male sex, especially in the age groups between 5 and 59 years, the figures being 1.54 and 1.34, respectively.Necropsy statistics are, of course, much more reliable. Among 6000 consecutive necropsies, recently analyzed by Courville, on the basis of experience in the Los Angeles General Hospital, brain tumors were found in about 1% of the cases. 2 Mental disturbances are present at one time or another in the great majority, if not in all, cases of intracranial tumor; and in some cases they are among the earliest manifestations. 3 However, relatively few