The health and nutritional status of a population generally improves and fertility rates fall during the process of socioeconomic development. Similarly, the nations of the world exhibit in cross section a strong nega­ tive association between health and nutrition, on the one hand, and fertility on the other.1 Clearly, these three are part of the interrelated processes of household and societal changes that occur during socio­ economic development. In this chapter we shall look at the evidence to determine to what extent relations among them are directly or indirectly causal, so that alterations in nutrition or health or the factors that influ­ ence them might be expected to alter fertility in a predictable direction.