This editorial summarizes new evidence, some of which is published in this supplement, on birth spacing and newborn, infant, child and maternal health, as well as the demand for birth spacing services in the developing world. The article points to the high number of annual infant, child and maternal deaths, low birth weight infants and malnourished infants and children in developing countries. It highlights several new findings on birth spacing relevant to these conditions: It argues that, in light of the new evidence, birth spacing is an important, feasible and practical intervention to address these conditions and should be included in developing country health programs.