A growing body of evidence points to the complexity of sexual behaviour. HIV risk behaviour is influenced by factors at three levels: within the person, within the proximal context (interpersonal relationships and physical and organisational environment) and within the distal context (culture and structural factors). This paper presents the findings of a review of research on the factors promoting and perpetuating unsafe sexual behaviour in South African youth. Papers included in the review were dated between 1990 and 2000 and addressed sexual behaviour of youth between the ages of 14 and 35 years. Both published works and unpublished reports and dissertations/theses were included. The review concluded that at least 50% of young people are sexually active by the age of 16 years; the majority of school students who had ever experienced sexual intercourse reported at the most one partner in the previous year, with a persistent minority of between 1% and 5% of females and 10-25% of males having more than four partners per year; and between 50% and 60% of sexually active youth report never using condoms. In terms of explanations for unsafe sexual behaviour among South African youth, the findings illustrate the powerful impact of the proximal and distal contexts, and in particular, the pervasive effect of poverty and social norms that perpetuate women's subordination within sexual relationships. Personal factors and the proximal and distal contexts interact to encourage HIV risk behaviour in ways that are not fully captured by social-cognitive models. The findings will be of interest to researchers and practitioners in the fields of adolescent sexual behaviour and HIV prevention in developing countries.