Study subjects were followed throughout the rainy season. Mothers/guardians were encouraged to take their child to the RVH OPD clinic or the health centre identified as being closest to their home at any time after discharge if the child became unwell. Project staff were based at each of these health centres, initially to identify children in the trial and to ensure that they were seen, properly investigated and treated promptly by health centre staff. At each visit axillary temperature was recorded using a digital thermometer. A dipstick for diagnosis of malaria was used to guide treatment if fever (axillary temperature of > 37.5°C) or history of fever within the previous 48 hours is present. In addition, a thick blood smear for malaria parasites was collected for subsequent confirmation of the diagnosis. Filter paper sample to test for S/P resistance were collected from all malaria cases detected during morbidity surveillance. Study subjects with documented fever (axillary temperature of > 37.5°C) or history of recent fever and malaria parasitaemia were treated with S/P and chloroquine. The treatment of study subjects seen at the health centres was the carried out by health centre staff in accordance with national guidelines. Study patients who needed admission were referred to RVH paediatric unit or the MRC ward.