The Santiago Young Adult Reproductive Health Survey was conducted in 1988 to examine the sexual behavior of and contraceptive use among young adults in Chile. The survey was based on multistage household probability samples of 865 women and 800 men aged 15-24 who were living in Santiago in 1988. Findings show that 35 percent of females and 65 percent of males had had premarital intercourse. Among those who had done so, the median age at first experience was 18.4 years for women and 16.4 years for men. Only 20 percent of females and 19 percent of males used contraceptives at first premarital intercourse. Use of contraceptives increased with age at the time of that event. Fertility data reveal that 70 percent of first births were premaritally conceived, and more than one-third of these were born prior to union. The high rates of premarital and unintended pregnancy among young women and the low prevalence of effective contraceptive use indicate a need for greater emphasis on sex education and family planning services directed at adolescents and unmarried young adults in Santiago.