The British government established the Teenage Pregnancy Unit in 1999 to reduce early pregnancy. Current policy initiatives have a significant geographic dimension: specific English neighbourhoods have been identified as the sites where most early pregnancy occurs and have been targeted for intervention. The aim of this thesis is to explore the factors that influence teenage sexual and reproductive behaviour by drawing on the neighbourhoods effects literature. Within this body of research, teenage reproduction is believed to be affected by a multiplicity of factors operating within different domains. The analysis (of survey data and qualitative material collected in three locations) was guided by two research questions: which factors within neighbourhoods, family and peer contexts are the most important in elucidating the causal pathways to teenage sex, pregnancy and fertility; and do the importance of these factors vary between neighbourhoods? Overall, factors within neighbourhood and peer contexts were found to be less significant than family and individual-level factors. The analysis of British Cohort Study data showed that, for example, women who experience teenage pregnancy or birth lived in deprived areas at age 16, but other neighbourhood variables were not significant in multivariate analysis. There were some differences between neighbourhoods, but the cohort member's attitude to school was, generally, the most important factor associated with teenage sexual and reproductive behaviour. The qualitative data supported these statistical results. There was little evidence that women had been influenced by either their friends or others within their neighbourhoods (though some women reported knowing high numbers of teenage mothers), and nearly all the young mothers had low educational attainment. In conclusion, individual and family-level influences on sexual and reproductive outcomes are paramount, but behaviour is also subtly informed by wider social factors.