BACKGROUND: Adolescent men who have sex with men (AMSM) have a high rate of HIV diagnoses. An estimated 14.5% of HIV infections in the United States are undiagnosed; but among 13-to 24-year-olds, the rate is 51.4%. We describe HIV testing rates and identifies salient individual, family, school, and health care influences among AMSM.METHODS: Data were collected as part of SMART, an ongoing pragmatic trial of an online HIV prevention intervention for AMSM (N = 699). Measures included lifetime HIV testing, demographics, sexual behaviors, condom use, HIV education from school and family, sexual health communication with doctors, HIV knowledge, and risk attitudes.RESULTS: Only 23.2% of participants had ever had an HIV test. Rates of testing increased with age (5.6% in 13-to 14-year-olds; 15.8% in 15-to 16-year-olds; 37.8% in 17-to 18-year-olds), and sexual experience was a strong predictor of testing (odds ratio: 6.54; 95% confidence interval: 3.95-11.49; P , .001). Most participants had a regular doctor (67.5%), but few had conversations about same-sex sexual behaviors (21.3%), HIV testing (19.2%), or sexual orientation (29.2%). Speaking to a doctor about HIV testing had a large effect (odds ratio: 25.29; confidence interval: 15.91-41.16; P , .001), with 75.4% who had such conversations having been tested, compared to only 10.8% of those who had not had such conversations.CONCLUSIONS: Despite higher risk, few participants reported ever having received an HIV test. Data indicate pediatricians are an important, but largely untapped, source of testing and could be integral to achieving testing rates needed to end the epidemic.WHAT'S KNOWN ON THIS SUBJECT: An estimated 14.5% of HIV infections in the United States are undiagnosed; but among 13-to 24-year-olds, the undiagnosed rate is .3.5 times greater (51.4%). This disparity is due to poor testing rates among those ,18 years old.WHAT THIS STUDY ADDS: Few studies describe HIV testing rates among minors (,18 years old), opting to group minors with adults. Focusing on this youngest group reveals opportunities for pediatricianadolescent communication about sexual orientation and HIV, greatly increasing the odds of testing.