Data are assembled from previously published studies from the Health Insurance Plan of Greater New York, the Eastern Health District, Baltimore, and several Scandinavian sources which relate to age-specific prevalence and incidence of neuroses. The age curve for new cases and that for all diagnosed cases at a given time rise rapidly during early adult life and then decline at older ages. There is limited evidence to suggest that neurotic illnesses are characteristic of a particular period of the life span and are, in the mass, of short duration. The need for further study is emphasized.