The purpose of this research study is to find out how well chloroquine works as a drug to treat malaria in children, compared to the standard malaria treatment in Malawi. In preparation for a longer study of the malaria treatment medication chloroquine alone and in combination with other drugs, a shorter pre-study will be done to compare the anti-malarial effectiveness of chloroquine versus sulfadoxine-pyrimethamine (SP), the standard treatment in Malawi. Two hundred ten children, ages 6 months to 12 years, around Blantyre, Malawi, will be given standard dosing of either chloroquine or SP when they come to the Ndirande Health Centre with signs or symptoms consistent with malaria. The first 30 participants in each treatment group will remain under continuous observation at the health center so that the researchers can monitor their response to the medication until the infection goes away. The participants will be followed for 28 days to see if the the treatment works or fails.