Antimalarial chemoprophylaxis can reduce morbidity and mortality from malaria in children. However, this approach to malaria control has not been implemented widely because of concerns over its possible effect on the development of resistance and natural immunity. Intermittent preventive treatment (IPT) may be able to achieve some of the beneficial effects of chemoprophylaxis without its drawbacks. Recently, it has been shown that IPT given to Senegalese children under the age of five years on three occasions during the malaria transmission season reduced the incidence of clinical malaria by approximately 90%. However, it is uncertain how this intervention can be most effectively delivered. Therefore, 26 Maternal and Child Health (MCH) trekking clinics in Upper River Division, south of the River Gambia, each with an average catchment population of 400-500 children under 5 years of age, will be randomly allocated to receive IPT from the MCH trekking team or from a IPT dispenser (village health worker, traditional birth attendant or a community mother based in a primary health care village). Treatment with a single dose of sulfadoxine /pyrimethamine (SP) plus three doses of amodiaquine will be given to all study subjects at monthly intervals on three occasions during the months of September, October and November. The primary end points will be the incidence of clinical attacks of malaria detected by passive case detection, and cost-effectiveness of the delivery methods. Important secondary endpoints will be the coverage and the equity of coverage of IPT in preventing malaria morbidity.