Following consent to participate, children visiting the Bandim Health Centre on the outskirts of Bissau with mono-infection with Plasmodium falciparum are by block-randomization allocated to one of the four different treatment groups. The treatment is given supervised by one of the health workers. The children are visited and malaria films obtained on day 2 and day 7 and then once weekly until day 35. On day seven, 100 microliters of capillary blood are drawn for analyses of chloroquine or amodiaquine concentrations in whole blood. Whenever a child has recurrent parasitaemia, a filter-paper blood-sample is collected for later PCR analysis.