Young adults, particularly young gay men (YGM), are vulnerable to human immunodeficiency virus (HIV). Yet, little is known about how YGM discuss sexual health issues with their friends ("gay boy talk"). We conducted semi-structured interviews with YGM and their best friends (11 YGM/YGM dyads and 13 YGM/heterosexual female dyads). In this paper, we examine risk assessment assumptions conveyed within YGM's communication about sexual health with their friends and how, if at all, the sexual scripts guiding these assumptions may differ between YGM and young women. Findings demonstrated that, while these young adults clearly intended to support their friends and promote safer sex, they also conveyed assumptions about HIV risk assessment, especially regarding sexual partner selection, that may actually increase their friends' risk for HIV infection. Since inaccurate HIV risk assessment assumptions were transmitted via sexual health communication between peers, it is suggested that such assumptions may need to be addressed in HIV prevention programs working with YGM and their friends. Further, gender differences were identified within the sexual scripts shared between YGM and their friends, suggesting that such interventions should be tailored to the specific needs of different friendship networks.