The objective of this research is to examine the relationships between young people's sexual knowledge, sexual subjectivities and (hetero)sexual practices. It also aims to investigate how young people's articulation and experiences of their sexual knowledge, subjectivities and practices are gendered. A further goal is to re-examine what is theorised as a 'gap' between young people's knowledge and practice. The research sample consists of 515 New Zealanders aged 17-19 years drawn from schools and community training programmes within the Auckland and Hamilton regions. A feminist research methodology is employed utilising a combination of quantitative and qualitative methods in order to explore different narratives produced in diverse research contexts. These contexts include 17 focus groups, 12 individual interviews, 6 couples engaging in a specially designed 'activity', and the distribution of 411 questionnaires. Contribution is made to the literature on sexuality education by re-visiting the 'gap equation' so that primacy is given to young people's own construction of the concepts of 'knowledge' and 'practice' and the perceived relationships between them. The research methods employed afford young people agency by enabling them to review this 'gap' from their own perspective. Young people's agency is also revealed by in-depth exploration of their sexual subjectivities and particularly how their subjectivities are constituted through dominant discourses of heterosexuality. How alternative sexual subject positions are negotiated by young people, and the contexts and factors which make this possible, are also investigated. The research extends our understanding of sexual subjectivity by taking account of young people's 'materiality', as it is expressed in their talk about their experience of their bodies in relation to sexuality. The research thus reveals how the processes of embodiment and disembodiment are experienced differently by young men and women and identifies another bodily state known as dys-embodiment. The gendered nature of these corporeal states are explained through use of the concept of the 'imaginary body'. On the basis of the sample, the findings suggest there is a difference between young people's construction of sexual knowledge and how it has been conceptualised by sexuality educators and academics. Young people's gendered relationships to knowledge and the implications these have for their (hetero)sexual practice are described. Subjects in this study talk about knowledge in two ways; as information derived from secondary sources such as sexuality education and knowledge gleaned from personal sexual experience. Hierarchies can be seen within and between such types of sexual knowledge in terms of the status young people afford, and interest they display, in them. Sexual practice as conceptualised by young people appears not to simply involve 'correct' sexual behaviour and safer sex practices, but also a 'discourse of erotics'. The research illustrates this discourse by exploring what young people do and do not find pleasurable about sexual activity, along with details about their relationships. The 'sexualisation' of power within the context of a couple . relationship is described and an analytic framework which traces 'equal', 'mediated' and 'coercive' power is devised. Such findings have important ramifications for the future design of sexuality education programmes. They point to the need for further exploration of how such insights about sexual knowledge, subjectivities and practices might be translated into effective sexuality education programme design.