This thesis provides an account of the interplay between the economic, demographic and religious factors which influence women's age at first marriage, their adoption of contraception and their fertility, in a group of rural communities in southern India. In so doing, it also assesses possible implications for state-level population policies in India, which may need to take into account differences in nuptiality, contraceptive adoption and fertility across religious groups. Religion is conceptualised as affecting demography in two ways: first, through its philosophical content or 'particularised theology', and second, in terms of `characteristics' or socio-economic differences between members of different religious groups. The focus of this study is Hindu-Muslim demographics in south India. Hence, the 'particularised theology' component is dealt with by undertaking, in Chapter I, a detailed comparison of the philosophical content of Islam and Hinduism on marriage, birth control, the position of women, and the importance of children within the family. The main finding is that with the exception of provisions on birth control, there is little difference between Hinduism and Islam in their theological positions on demographic issues. The 'characteristics' component is dealt with by including socio-economic variables in the econometric models. The aim is to investigate whether there are any differences across religions in the age at marriage, fertility and the decision to use contraception, after controlling for various economic, social and biological factors.