The socio-economic and family background and the nutrition of 145 children with kwashiorkor admitted to hospital in Khartoum over a 2-year period were compared with 113 marasmic kwashiorkor, 158 marasmic, and 186 nutritionally normal controls of similar age. Peak admissions for kwashiorkor were in the wet and post-wet season and the mean (SD) age was 1.6 (0.6) months. Mothers of malnourished children were more likely to be pregnant, and had poorer housing, sanitation and water supply, a lower income and food expenditure and less education than controls. Mothers of controls breastfed their children longer, introduced mixed feeding earlier, offered a wider variety of foods, and were more likely to have had their infants immunized. Neither family instability nor cultural practices which result in separation of children from their mothers appear to have an important role in protein-energy malnutrition in the Sudan. Families of kwashiorkor children had a higher food expenditure and better maternal education than marasmic children. There was no significant difference between the two groups in duration of breastfeeding or in the age of introduction of mixed diet. However, kwashiorkor children appeared to be offered more meat. Differences in food availability could account for the relative retardation of growth and lack of subcutaneous fat in marasmus compared to kwashiorkor.