Purpose: This paper seeks to explore the theoretical bases for teacher-delivered and peer-delivered sexual health promotion and education. Design/methodology/approach: The first section briefly outlines the main theories informing sexual health interventions for young people, and the second discusses their implications for modes of delivery. Findings: Most interventions that claim to be theoretically based draw on social-psychological cognition theories. Other programmes aim to develop self-esteem and/or empowerment, while the two main sociological ideas underpinning sexual health programmes are the gendered construction of sexuality and the diffusion of innovations. Research limitations/implications: More research is necessary to clarify the mechanisms by which sexual health promotion works, which in turn should contribute to more empirically based theory. Practical implications: If theoretical ideas are to be translated into potentially effective programmes, the specific features of the setting, target group and those delivering the programme must be taken into account. Originality/value: This paper compares the theoretical justifications for different modes of delivering sexual health promotion, through outreach peer educators, formal school-based peer educators and teachers. (Contains 1 table.)