BACKGROUND: Human immunodeficiency virus (HIV) infections are increasing among young men who have sex with men (YMSM), yet few HIV prevention programs have studied this population. Keep It Up! (KIU!), an online HIV prevention program tailored to diverse YMSM, was developed to fill this gap. The KIU! 2.0 randomized controlled trial (RCT) was launched to establish intervention efficacy. OBJECTIVE: The objective of the KIU! study is to advance scientific knowledge of technology-based behavioral HIV prevention, as well as improve public health by establishing the efficacy of an innovative electronic health (eHealth) prevention program for ethnically and racially diverse YMSM. The intervention is initiated upon receipt of a negative HIV test result, based on the theory that testing negative is a teachable moment for future prevention behaviors. METHODS: This is a two-group, active-control RCT of the online KIU! intervention. The intervention condition includes modules that use videos, animation, games, and interactive exercises to address HIV knowledge, motivation for safer behaviors, self-efficacy, and behavioral skills. The control condition reflects HIV information that is readily available on many websites, with the aim to understand how the KIU! intervention improves upon information that is currently available online. Follow-up assessments are administered at 3, 6, and 12 months for each arm. Testing for urethral and rectal sexually transmitted infections (STIs) is completed at baseline and at 12-month follow-up for all participants, and at 3- and 6-month follow-ups for participants who test positive at baseline. The primary behavioral outcome is unprotected anal sex at all follow-up points, and the primary biomedical outcome is incident STIs at 12-month follow-up. RESULTS: Consistent with study aims, the KIU! technology has been successfully integrated into a widely-used health technology platform. Baseline enrollment for the RCT was completed on December 30, 2015 (N=901), and assessment of intervention outcomes is ongoing at 3-, 6-, and 12-month time points. Upon collection of all data, and after the efficacy of the intervention has been evaluated, we will explore whether the KIU! intervention has differential efficacy across subgroups of YMSM based on ethnicity/race and relationship status. CONCLUSIONS: Our approach is innovative in linking an eHealth solution to HIV and STI home testing, as well as serving as a model for integrating scalable behavioral prevention into other biomedical prevention strategies. TRIAL REGISTRATION: Clinicaltrials.gov NCT01836445; https://clinicaltrials.gov/ct2/show/NCT01836445 (Archived by WebCite at http://www.webcitation.org/6myMFlxnC).