The purpose of this study is to measure the direct and indirect relationships between socio-economic and demographic variables and ideal and desired family size preferences among male and female high school seniors in Utah in 1974. Furthermore, the analysis will be carried out separately for males and females in order to see if male and female ideal and desired family size preferences are influenced differently by the socio-economic and demographic variables. A model will be developed and tested of the process by which ideal and desired family size preferences are formulated. The model used in the analysis is based upon Westoff and Potvin's "theory of ideal family size formation." Westoff and Potvin's "theory of ideal family size formation" states family size of female's is a result of early socialization. The socialization can be influenced by four categories of processes. The four categories are family size in e nvironment variables, social context variables, consistency and continuity in life experiences, and interaction between beliefs and behavior. The socio-economic and demographic variables selected to test this model were size of family of orientation, place of residence, social class, religion, religiosity, desired age at marriage , ideal age at marriage, the number of circumstances females or males would consider acceptable for the use of birth control, and education difference. The application of Westoff and Potvin 's "theory of ideal family size formation" was a better fit for desired family size of females or males than ideal family size of females or males. Desired family size of females was influenced by religion, religiosity , size of family of orientation, and the number of circumstances females/males find acceptable for the use of birth control. Desired family size of females was also influenced by social class. Ideal family size of females is different from ideal family size of males. Both ideal family size of f emales and males was influenced by religion. Ideal family size of males was al so influenced by religiosity and social class. The given socio-economic and demographic variables explained 39 percent of the variation for female desired family size and 29.5 percent of the variation for male desired family size. The given socio-economic and demographic variables explain 4 percent of the variation for female ideal family size and 17 percent of the variation for male ideal family size.