Antiretroviral therapy (ART) has improved survival for those living with HIV. However, low-level ART adherence can impede viral suppression, which presents a major public health challenge due to the probability of further HIV transmission. In the U.S., gay, bisexual, and other men who have sex with men (GBMSM) accounted for 70% of new HIV infections in 2014. What is more concerning is that 60% of HIV-positive GBMSM are not adherent to ART. Further, disparities exist among HIV-positive minority racial/ethnicity GBMSM, who are less likely to be engaged in HIV care, are less adherent to their ART, and more likely to have detectable HIV viremia than White GBMSM. It has been established that ART adherence reduces HIV RNA levels in blood and semen, and studies show that viral suppression is associated with decreased transmission of HIV to sexual partners. This study is a supplement to the parent study (R01 MH100973), an online, video-based 2-arm intervention for 1,500 high-risk, virally unsuppressed or sub-optimally ART adherent U.S. HIV-positive GBMSM who are being followed for 12 months. In this supplement, we propose to use dried blood spot (DBS) kits to: verify participant self-reported viral load and quantify levels of HIV viremia among participants after 12-month follow-up. Recent online studies of GBMSM have shown relatively high uptake of home collection of biomarker data at an approximately 70% return rate. Improved DBS collection materials (HemaSpot?) have been developed, streamlining blood collection. To our knowledge, the proposed study would be the first to implement at-home DBS collection in a high-risk, HIV-positive GBMSM online study population using a state-of-the-art DBS collection device. The proposed supplement will increase the value of the parent project by: 1) determining the proportion of men enrolled in an online behavioral intervention who have an undetectable HIV viral load, post 12-month follow-up, 2) providing a comparison between laboratory-measured viral load and self-reported viral load, and 3) engaging priority populations (e.g., young minority HIV-positive GBMSM who experience health disparities) in healthcare/self-care-related activities.