Following village meetings, the families of all eligible children were contacted and asked if they wished their child to join the study. If they wished to do so, informed consent was obtained and the child randomised to one of four treatment arms. At the beginning and at the end of the malaria transmission season, children were examined and a finger prick blood sample was obtained for determination of haemoglobin and preparation of blood films for microscopy. A drop of blood was collected on filter paper for subsequent molecular studies.