Severe anaemia is a frequent cause of admission to hospitals in tropical Africa and about 10% of such children die. In endemic countries, anaemia has multiple causes such as nutritional deficiencies, infections and haemoglobinopathies. However, Plasmodium falciparum infection is believed to be the major contributory factor to the aetiology of severe anaemia. Severe anaemia is usually treated by blood transfusion although transfusion carries the attendant risk of transmission of HIV and other blood-borne infections. Thus, there is a need to explore novel strategies to reduce the incidence of severe anaemia in high-risk groups such as children with suboptimal haemoglobin levels because these children are at increased risk of developing severe anaemia if they develop a malaria infection before their haemoglobin level has normalized. Therefore, it is proposed to study whether monthly chemoprophylaxis with sulphadoxine/pyrimethamine (S/P) given during malaria transmission season can protect Gambian children from developing severe anaemia. After receiving treatment from the hospital, 1200 children admitted to the hospital with a haematocrit of less than 21% were randomised to receive either monthly S/P or placebo during the rest of the malaria transmission season. Morbidity was monitored throughout the rainy season. Study subjects were seen at the end of the dry season to document morbidity and mortality.