*Abstract:**We use data from the 2002-2013 National Surveys of Family Growth toexamine change across U.S. cohorts born between 1966 and 1995 in whetherindividuals have had sex with same-sex partners only, or with both men andwomen, and in whether they have a bisexual or gay identity. Adjusted forage, race/ethnicity, immigrant status, and mother’s education, we findincreases across cohorts in the proportion of women who report a bisexualidentity, who report ever having had sex with both sexes, or who reporthaving had sex with women only. By contrast, we find no cohort trend formen; roughly 5% of men in every cohort have ever had sex with a man, andthe proportion claiming a gay or bisexual attraction changed little. Inconcluding, we speculate that the gender difference is rooted in a broaderpattern of asymmetry in gender change in which departures from traditionalgender norms are more acceptable for women than men.*