The onset of puberty is a critical moment for reaching girls with health messages and information, and the stakes are particularly high in countries where the HIV/AIDS epidemic rages and where threats to female reproductive health abound. Yet to date, the healthcare community in low-resource countries has tended to neglect this opportunity and instead concentrate efforts on young women who are older and of reproductive age. A multi-year project in Tanzania, the Girl’s Puberty Book, addresses this gap.