• We surveyed all neurologists, ophthalmologists, and neurosurgeons in Iowa, eastern Nebraska, and Louisiana over one year to determine the annual incidence of pseudotumor cerebri in residents of Iowa and Louisiana. The results were similar for both states. In Iowa, the annual incidence in the general population was 0.9 per 100 000 persons. When obesity was considered, this increased the incidence to 13/100 000 persons in Iowa and 14.85/100 000 persons in Louisiana for women 20 to 44 years of age who were 10% or more over ideal weight. Furthermore, the incidence became 19.3/100 000 for women in the same age range when they were 20% or more over ideal weight. The female-to-male ratio was 8:1, and the mean weight was 38% above ideal weight for height. Pseudotumor cerebri is a relatively common neurologic illness and may be an important preventable cause of blindness in obese young women.