Intermittent Preventive Treatment of malaria in infants is a promising strategy to reduce incidence of clinical malaria in children under the age of 1 year. It is likely to be implemented as a malaria control strategy in Tanzania using sulfadoxine/pyremethamine SP. SP is failing as a first line treatment for clinical episodes of malaria and government policy is driving a change to use Artemesin Combination Therapy (ACT). The main ongoing Kilimanjaro IPTi study is looking at alternatives to SP for use in IPTi. Currently, as there is no evidence for the use of other drugs for IPT, SP will be continued for IPT in pregnancy and in infants. This study proposes to measure the efficacy of SP and chlorproguanil/dapsone (CD), in symptomatic 6- 59 month old children using standard methodology. These are both study drugs in the main IPTi study. This will help us to see how the efficacies of SP and CD in sick children relate to the efficacies for treating asymptomatic children with IPTi. In addition this proposal aims to test the efficacy of SP given to 2-10 month old asymptomatic infants (the target group for IPTi). Evidence suggests that asymptomatic malaria infections with low parasitaemia have a higher cure rate than symptomatic infections with high parasitaemia even when markers of resistance are highly prevalent. This second study aims to quantify this difference and will produce evidence to help policy makers know when drugs used for IPTi should be changed. Both studies will be open label and run concurrently in Hale, Korogwe district near to the main Kilimanjaro IPTi site in Tanzania.