Two drug strategies for the control of malaria in children aged 3-59 months have been compared in a rural area of The Gambia--treatment of presumptive episodes of clinical malaria with chloroquine by village health workers, and treatment combined with fortnightly chemoprophylaxis with 'Maloprim' (pyrimethamine/dapsone) which was also given by village health workers. Treatment alone did not have any significant effect on mortality or morbidity from malaria. In contrast, treatment and chemoprophylaxis reduced overall mortality in children aged 1-4 years, mortality from probable malaria, and episodes of fever associated with malaria parasitaemia. A high level of compliance with chemoprophylaxis was obtained and no harmful consequences of chemoprophylaxis were observed.