Some single Caucasian undergraduates of Protestant religious preference, 115 men and 105 women, were tested to find correlates of, and to compare social-psychological to demographic variables in predicting, subjects' desired family sizes. Men had a mean desired family size of 2.04 children and women, 1.91 children. Women seem more accepting of childless families than men, perhaps perceiving new attractiveness in careers. Men and women wanting small families are less religious and are from smaller families. These men are more anxious and lower in need achievement, and the women have a less traditional sex-role self-concept. Women may see larger families as confirming a traditional sex-role, while men may see them confirming an achievement-oriented, possibly traditional, male role. Demographic variables, which best predict desired family size, may represent the continued influence of subjects' family backgrounds. However, social-psychological variables may also become important desired family-size influences as women enter their early twenties.