Objective: The current study examined conceptions of adulthood, close personal relationships, and health behaviors (dietary intake, substance use, sexual behaviors) of emerging adults aged 18-30 with horizontally-infected HIV. Emerging adults were expected to differ in levels of achievement of adulthood tasks. The quality of close relationships, and perceptions of close friends’ behaviors were hypothesized to be associated with health behaviors. Method: Utilizing a cross-sectional design, 48 emerging adults with HIV (64.6% female; M age = 22.59, SD = 3.17) from a youth-based clinic serving most of Miami-Dade County were recruited. Participants completed measures on markers of adulthood, close friend and romantic partner qualities, health behaviors, and perceptions of close peers’ health behaviors using Filemaker technology on laptops; audio computer-assisted self-interview options were available. Results: The domains of individualism and family capacities received the highest mean ratings of importance for marking adulthood. Participants rated the acceptance of responsibility for one’s actions and making independent choices as being most important for being considered an adult; other items rated highly were related to emotional control and adopting new family roles. In the domain of peer relationships, participants who had a close friend or romantic partner generally reported high levels of positive qualities in the friendship that were comparable to national samples; however, most individuals had not disclosed their HIV status to their best friend or romantic partner. A number of emerging adults (12.5%) reported having no friends, which is a higher percentage of friendless individuals than national samples. Most emerging adults with HIV reported consumption of fewer fruits and vegetables than national recommendations. In addition, comparable to rates found among adolescents and emerging adults without HIV, participants were engaged in substance use and risky sexual practices such as having multiple sexual partners. Conclusions: There was considerable variability in development among emerging adults. Conceptions of adulthood and peer relationships may be a particularly important aspect of development to examine among emerging adults with HIV. In addition, many of these individuals continue to engage in health risk behaviors that may require intervention efforts geared specifically to their developmental stage. Implications for care providers are discussed.