Research has consistently shown that, compared to men, women are more cautious and selective and maintain greater marital aspirations in entering and maintaining sexual relationships. One explanation of this sex difference is that women have traditionally had inferior access to earning power and social status and consequently were forced to acquire socioeconomic status (SES) through their choice of marriage partners. A contrasting view is that this difference is a component of the basic sex difference identified in the Kinsey studies: Men are more likely than women to dissociate coitus from emotional attachment and to desire and seek coitus with a variety of partners. These two explanations were explored in open-ended interviews with matched samples of 20 male and 20 female medical students. The results were more consistent with the perspective of basic sex differences than with the differential resources explanation. Increasing female SES does not appear to eliminate or even substantially reduce this sex difference. Increasing SES tends to enlarge the pool of acceptable, available sexual and marital partners for men while it tends to reduce the pool for women. Increasing SES thus tends to have different effects on men and women and may cause sex differences in the tendency to associate coitus with emotional attachments and marital aspirations to be more, rather than less, apparent. Extensive case data with verbatim quotations are presented to reveal the emotions and desires underlying subjects' overt behavior.