A survey was made of studies reporting population prevalence rates for the different types of neurotic disorders in order to determine the utility of these rates for familial and genetic research. Rates varied considerably among studies both for all neuroses and for particular types of neuroses, even among studies using similar methods examining similar populations. The method of case ascertainment (personal interview
versusrecord searches) and the threshold for defining an individual as affected are important contributors to variation. The use of the published prevalence rates for quantifying familial and genetic effects on the neurotic disorders would be premature.