Harnessing the power of text messaging to reduce HIV incidence in adolescent males across the United States - Sexual minority male youth face disparate risk for HIV acquisition. Disparities are even starker for African American/Black and Hispanic sexual minority male youth, who account for 51% and 25% of new HIV infections, respectively. Youth living in southern states and in rural settings also face elevated risk for HIV acquisition. As such, access to HIV testing and counseling remains a critical component of prevention, and effectively extending these services to sexual minority male youth is a priority. The wide adoption of text messaging provides novel opportunities to go where youth “are” across socio- demographically different groups, and overcomes structural challenges of traditional interventions. Moreover, being able to access sensitive content when and where one chooses facilitates safe spaces for youth to engage with the content, which is important for those who are not ‘out’. Importantly too, reviews suggest that programs delivered via text messaging can affect complex behavior change, including HIV testing among sexual minority adolescent boys. Thus, we have the opportunity to utilize the power and reach that text messaging affords to deliver an HIV prevention program across the country to a diverse population of youth. To this end, we propose to test the impact of #GrowingUpGuy (#GUY) on new HIV infections among 13-20 year-old sexual minority male youth across the United States. #GUY will be an adaptation of the research team’s previous text messaging-based HIV prevention/healthy sexuality programs developed at the national level for sexual minority youth. Given the epidemiology of HIV infections in the United States, we plan to target youth 13-20 years of age. Because of the lack of accessible programs for younger youth, our recruitment effort will place an emphasis on those 18 years of age and younger. Sample diversity will be ensured using recruitment targets and a complex enrollment strategy that we have developed and refined over our intervention endeavors such that half will self-identify as Black/African American, Latino, and/or of mixed race; and at least 20% will be living in a rural area or southern state. Specifically, we aim to: Specific Aim 1: Finalize the GrowingUpGuy (#GUY) intervention and protocol for sexually active, HIV negative, cisgender, sexual minority boys and men up to 20 years of age across the United States. Specific Aim 1a. Adapt previous intervention content to create GrowingUpGuy (#GUY), a salient, technologically delivered HIV prevention program. Specific Aim 1b: Finalize the intervention protocol, including confirmation of HIV test results. Specific Aim 2: Test the #GUY intervention for impact on HIV incidence (n=5,000). Our main outcome measures will be: 1) OraQuick-confirmed HIV incidence; and self-reported 2) PrEP and PEP use, 3) HIV status, and 4) number of STIs. Secondary outcomes include: 1) information about and 2) motivation for uptake of PrEP; and 3) the impact of the intervention on mental health indicators.