THIS BOOK CONTAINS MY WRITING ON ECONOMIC GROWTH AND DEVELOPMENT, FROM THE MARSHALL LECTURES THAT I GAVE TO THE 1997 KUZNETS LECTURES, PUBLISHED HERE FOR THE FIRST TIME. THE GENERAL THEME OF THE COLLECTION IS THE ATTEMPT TO ADAPT MODERN GROWTH THEORY, ORIGINALLY DEVELOPED TO DESCRIBE THE BEHAVIOR OF THE INDUSTRIALIZED ECONOMIES, TO OBTAIN A UNIFIED UNDERSTANDING OF RICH AND POOR ECONOMIES ALIKE IN A WORLD OF VAST INCOME AND GROWTH RATE DIFFERENCES.