The primary trial end-point was the incidence of clinical attacks of malaria in children who received IPTc or placebo. Clinical malaria was defined as an episode of fever (temperature recorded to be 37.5 degrees Celsius or higher or a history of fever within the previous 24 hours) for which no other cause could be found and the presences of P. falciparum parasitaemia at a density of 3,000 parasites per microlitre or greater. This parasite density was chosen as it has been shown previously to be an appropriate fever threshold in the study area. Secondary end-points included the incidence of side effects in children in each group, changes in the prevalences of resistance markers and the incidence of clinical malaria in the year following the main trial.