Results. Data from the 2002 survey indicate that by age 20, 77% of respondents had had sex, 75% had had premarital sex, and 12% had married; by age 44, 95% of respondents (94% of women, 96% of men, and 97% of those who had ever had sex) had had premarital sex. Even among those who abstained until at least age 20, 81% had had premarital sex by age 44. Among cohorts of women turning 15 between 1964 and 1993, at least 91% had had premarital sex by age 30. Among those turning 15 between 1954 and 1963, 82% had had premarital sex by age 30, and 88% had done so by age 44. Conclusions. Almost all Americans have sex before marrying. These findings argue for education and interventions that provide the skills and information people need to protect themselves from unintended pregnancy and sexually transmitted diseases once they become sexually active, regardless of marital status.