Abstract: | Approximately 3 million teens are diagnosed with a sexually transmitted disease (STD) annually; STDs rates for American Indian young adults are among the highest of any racial/ethnic group. An important risk factor for STDs is early initiation of sex. In this study, we examined risk for early initiation with 474 American Indian youth ages 14–18, using 11 risk factors from three developmentally important microsystems (family, school, peers) along with several individual characteristics; a cumulative risk index was also calculated. Discrete‐time survival analyses showed that predictors of early initiation differed by gender. For young men, younger initiation of sex was predicted by lower grades, liking school less, having peers with less prosocial attitudes, a greater likelihood of having used alcohol or drugs at first sex, and having higher sensation‐seeking. For young women, earlier initiation was related to having mothers who had their first child at an early age and who had less formal education, to having parents who had divorced, dropping out of high school, using alcohol/drugs at first sex, and higher sensation‐seeking. Higher cumulative risk was associated with elevated risk of sexual initiation, although the degree of added risk varied with age for women. Cumulative risk deserves broader attention in understanding the early initiation of sexual intercourse. |