A 42-year-old hospital worker had a recrudescence of falciparum malaria after chloroquine therapy. Further adequate treatment with chloroquine given orally did not clear the infection. He was then given a combination of sulphadiazine and pyrimethamine, which produced a radical cure. This points to the possibility of chloroquine-resistant Plasmodium falciparum in Nigeria, an African country where this has been thought to be unlikely. Because of this and earlier reports, clincians should be on the alert to the possibility of chloroquineresistant P. falciparum in this area, and efforts should be made to establish or reject the presence of malarial parasites resistant to chloroquine in Africa.