Sudan presents an excellent opportunity for studying mortality conditions in poor countries. It is one of the 25 "least developed" countries by U.N. designation, most of whom have very little information on mortality and general health conditions. As the largest African country in area, Sudan is also a land of rich ecological contrast, stretching from desert areas in the North through savannah areas to dense equatorial jungle in the South. The northern portions are Arabic and Islamic, the southern portions black African. The 1955/56 census enumerated 597 tribes speaking some 115 languages. Aridity in the North and swamps in the South have retarded the development of these areas and fostered nomadism, population concentration is greatest in the middle belt and particularly along the Nile and its tributaries. This paper has since been published as: "Child Mortality Differentials in Sudan," by Abdul-Aziz Farah; Samuel H. Preston in, Population and Development Review, Vol. 8, No. 2. (Jun., 1982), pp. 365-383. http://links.jstor.org/sici?sici=0098-7921(198206)8%3A2<365%3ACMDIS>2.0.CO%3B2-4