In this study, we examine cohort trends in who did and did not delay sex until marriage for U.S. women born between 1938 and 1985 using Cycles 3-7 of the National Survey of Family Growth. We find that roughly half of women born in the late 1930s and early 1940s were already sexually active prior to marriage. Especially rapid increases in not delaying sex until marriage occurred for women born between 1942-43 and 1954-55, with subsequent cohorts experiencing less rapid increases and with premarital sex reaching a plateau of roughly 85 to 90 percent for those born after 1962. Our continuous-time competing-risk models illustrate the methodological dangers of using single-decrement procedures for questions such as who did and did not delay sex until marriage. More generally, our findings suggest that the decoupling of sex and marriage was underway well before the so-called "sexual revolution" of the late 1960s and early 1970s.