In this presentation, Sir Partha Dasgupta explains the interface in poor countries of population growth, rural poverty, and deterioration of the local natural-resource base, a subject that has been much neglected by modern demographers and development economists. He analyzed the motivations for procreation in rural communities of the poorest regions of the world and summarized recent work on the relevance of gender relationships to such motivations. He also identified four potentially significant social externalities associated with fertility behavior and use of the local natural-resource base.