In the context of the recent controversy and confusion around sex education in Britain, I argue that an understanding of how boys and girls talk about sex and an awareness of the different and changing social worlds boys and girls inhabit, are crucial starting points for formulating sex education policies. Sex education is often embarked on without adequate understanding of the social context of sexuality and of the significance of changes in sexual practice that have occurred over the past few decades. Drawing on interviews and group discussion with male and female adolescents, I illustrate the difficulty boys and girls have communicating with each other and how for boys, to be intimate is to forego their dominance. I argue that there is a need to develop ways in which the power relations between boys and girls can be addressed and the derogatory way menstruation, pregnancy, and girls are perceived by boys can be challenged.