Amodiaquine is one of the possible alternative therapeutic options to treat chloroquine-resistant Plasmodium falciparum infections in Africa. In this study, its efficacy to treat patients with acute uncomplicated falciparum malaria and high parasitaemia (> or =5% of infected erythrocytes in the peripheral blood) was assessed by using the standard protocol developed by the World Health Organization. The mean pre-treatment parasitaemia was 10.8% (range, 5.0-35%). All 32 patients who completed the study (four lost to follow-up) had an adequate clinical and parasitological response on day 14. As compared with the pre-treatment parasitaemia, the mean parasitaemia decreased by 97.8% on day 2 (two patients with negative smears) and 99.97% on day 3 (22 patients with negative smears; the other ten patients had low residual parasitaemia ranging from 24 to 400 asexual parasites/microl). Our results suggest that, in areas of stable transmission in Africa, hyperparasitaemic patients with uncomplicated malaria can be safely treated with oral amodiaquine provided that their clinical and parasitological responses are closely monitored for the first 3 days and controlled on day 7 and 14.