College student men (n = 185) and women (n = 244) rated how desirable certain characteristics are in an ideal sex partner within a long-term relationship. They reported personal beliefs and predictions about the other gender's preferences. Of the twenty-six items that comprised each measure, factor analyses yielded five subscales: Communication/Openness, Physical Attractiveness, Knowledge/Skill, Take Control, and Response/Drive. As hypothesized, men placed greater emphasis than did women on Physical Attractiveness and Response/Drive, whereas women, more than men, believed Knowledge/Skill was important. Men and women differed completely on what they thought was important to each other. Furthermore, men recognized that there were gender differences on all subscales but Knowledge/Skill, whereas women recognized gender differences on all subscales. When the actual responses of men and women were compared with the beliefs that each had about the other, results showed that both genders underestimated the importance the other placed on Communication/Openness and overestimated that of Physical Attractiveness. Results are discussed with regard to implications for counselors.