The interaction between religion and fertility is the subject of intense debate in developing countries. This paper puts forward a new theory to provide an explanation for larger Muslim, relative to Hindu fertility, in the context of India. It does so by integrating the literature on missing women with that on religious di¤erences in fertility. Formally, the paper takes the notion of 'son preference'and the complementary concept of 'daughter aversion', linking them to religious di¤erences in fertility. Just as sons may bring 'bene…ts'to their parents, daughters may impose 'costs'. Consequently, the desire for sons may increase family size while the fear of daughters limits it. These two countervailing forces may act so as to determine equilibrium family size and composition. Econometric evidence is presented to test the theory using Poisson regression models estimated on a range of demographic variables relevant to this issue -the number of living children, the number of infant deaths and the sex ratio -estimated on data from a nationallyrepresentative sample of Indian women who had adopted a terminal method of contraception. The analysis concludes that higher Muslim fertility in India may be related to signi…cantly lower levels of daughter aversion among this community, bringing in to focus the interactions between religion, gender bias, and fertility behaviour. JEL Classi…cation Code: C25, J13, J15, O53, Z12