Importance  Despite similar sexual activity rates among male and female adolescents, males are more likely to have their first sexual intercourse before age 13 years. The developmental needs and pathways to healthy trajectories for young males remain unknown.

Objective  To examine the prevalence of sexual intercourse before age 13 years among male adolescents; the variation by race/ethnicity, location, and maternal educational level; and the wantedness of this first sexual experience.

Design, Setting, and Participants  This cross-sectional analysis was conducted from September 2017 to June 2018, using pooled 2011, 2013, and 2015 data from the school-based Youth Risk Behavior Surveillance System (YRBSS) and the 2006 to 2015 data of males aged 15 to 24 years from the household-based National Survey of Family Growth (NSFG). The percentage of males reporting sexual onset before age 13 years was estimated using survey-weighted logistic regression to test for differences by race/ethnicity within each national survey and within metropolitan areas (for YRBSS, high school and middle school samples). Among NSFG survey respondents, differences in wantedness of first sexual intercourse by age at first sexual intercourse were examined, along with the associations between sexual initiation and socioeconomic covariates.

Main Outcomes and Measures  Sexual onset before age 13 years.

Results  Data from a total of 19 916 male high school students (from YRBSS) and 7739 males aged 15 to 24 years (from NSFG) were included in the analysis. The sample was largely composed of non-Hispanic white males: 8789 (57.1%) from the YRBSS and 3737 (58.0%) from the NSFG. Sexual onset before age 13 years was reported nationally by 7.6% (95% CI, 6.8%-8.4%) of male high school students and 3.6% (95% CI, 3.0%-4.2%) of males aged 15 to 24 years. The proportion of male students who reported having sexual intercourse before age 13 years varied across metropolitan sites, from 5% (95% CI, 4%-7%) in San Francisco, California, to 25% (95% CI, 23%-28%) in Memphis, Tennessee, with elevated rates among non-Hispanic black and Hispanic males in most metropolitan areas. In the NSFG data set, respondents whose mothers had a college degree or higher educational level were statistically significantly less likely (OR, 0.31; 95% CI, 0.19-0.49) to report having sexual intercourse before age 13 years compared with those whose mothers did not have a college degree. Among males who reported having their first sexual experience before age 13 years, 8.5% (95% CI, 3.8%-17.8%) described their first sexual intercourse as unwanted.

Conclusions and Relevance  Rates of sexual onset before age 13 years among young males varied by race/ethnicity, location, and maternal educational level, presenting important implications for the provision of early, inclusive, and comprehensive sex education and sexual and reproductive health care to male children and adolescents.