Although the infant mortality rate is considered 1 of the preferred indicators for describing both demographic conditions and the overall and social economic well-being of a country, comparable and consistent estimates and projections of infant mortality for all countries of the world have been lacking.  In an attempt to improve this situation, the UN Population Division, with the support and encouragement of the UN Children's Fund and the assistance of the World Health Organization and the UN regional commissions, has recently completed a comprehensive project which provides estimates and projections of infant mortality for all world countries for the period 1950-2025.  This article reviews the estimates and projections produced by this project.  The various sources and the quality of the data, as well as the methods employed to estimate current and past levels of infant mortality and to project future trends, are reviewed and evaluated.  The article concludes with a discussion of the results vis-a-vis the goals set for infant mortality by the World Population Plan of Action and the International Development Strategy for the 3rd UN Development Decade.