The authors describe a patient with the cerebral form of tropical malaria. The diagnosis was made about one hour after admission to hospital, and owing to this it was possible to start successful treatment with 4-quinoline preparations. The clinical diagnosis was confirmed by examination of stained preparation of peripheral blood. It is stressed that manifestations of acute encephalitis regressed rapidly after administration of 4-quinolines, and that parasitaemia persisted for a long time after regression of the acute phase despite absence of objective and subjective abnormalities.