This paper is an ethnography of a four-year, multi-disciplinary adolescent sexual and reproductive health intervention in Bolivia, Nicaragua and Ecuador. An important goal of the intervention – and of the larger global field of adolescent sexual and reproductive health – is to create more open parent-to-teen communication. This paper analyzes the project's efforts to foster such communication and how social actors variously interpreted, responded to, and repurposed the intervention's language and practices. While the intervention emphasized the goal of ‘open communication,’ its participants more often used the term ‘confianza’ (trust). This norm was defined in ways that might – or might not – include revealing information about sexual activity. Questioning public health assumptions about parent–teen communication on sex, in and of itself, is key to healthy sexual behavior, the paper explores a pragmatics of communication on sex that includes silence, implied expectations, gendered conflicts, and temporally delayed knowledge.