There is abundant research on the links between family and household structure and young people's sexual risk-taking behaviours, but this scholarship although emerging in sub-Saharan Africa is largely limited to the West. Using data from the 2004 National Adolescent Survey conducted among 12-19 year olds in Ghana, and applying discrete time hazard models, this study examined the effects of household living arrangements on the timing of first sexual intercourse among adolescents in Ghana. The study also explored the extent to which parental monitoring and supervision mediates the effects of household living arrangements on age at first sex. Results indicate that young people who live alone, with grandparents or other households had a higher risk of first sex compared with those who lived with both biological parents. Much of this advantage, however, could be attributed to parental monitoring and household wealth. There were significant gender differences among Akan and non-Akans regarding the timing of sexual debut among young people in Ghana.