Children with symptomatic malaria in Bissau were randomly assigned to treatment with chloroquine 25 mg base/kg given supervised at a health centre or unsupervised by the mothers at home. On day 7, a blood sample for drug analyses was drawn and the children were then followed once weekly for 5 weeks. The data were analysed on an intention to treat basis. No differences were seen in the outcome of treatment nor in the blood drug concentrations on day 7 between the two groups. Mothers in Bissau can be trusted to give adequate anti-malarial medication to their children at home.