A series of peripheral blood films taken from Gambian children with either acute or low-grade Plasmodium falciparum infections were examined for abnormal features of the red and white cells. Hypochromia and polychromasia with cytoplasmic stippling were predominant features in both groups. Lymphocytosis, granulocytosis and plasmacytosis were common white cell abnormalities. An additional feature in films from patients with acute malaria was the presence of numerous atypical lymphocytes. A comparison of the features in the two groups indicated that some abnormalities are associated with an acute attack of malaria and that others have a nutritional or genetic aetiology.