Within the framework of its surveillance of Plasmodium falciparum chloroquine sensitivity in eight West African countries (Benin, Burkina Faso, Côte d'lvoire, Mali, Mauritany, Niger, Senegal, and Togo) the Reference Centre for Chemoresistant Malaria (CRCP) at the Organization for Coordination and Cooperation to Control Major Endemic Diseases (O.C.C.G.E.) conducted an in vivo survey in February, 1987, in Sokodé (Togo). Two groups of 67 children, aged 2 to 9, received, for the first group a single 10 mg/kg dose of chloroquine; for the second group a 3-day 25 mg/kg dose, according to the WHO methodology. Thick and thin blood smears were examined on D0, D2, D3 when necessary, D4 and D7. Within the 23 children who received the 10 mg/kg dose, seven (30.4%) presented a "resistance", of which six were early RI type and 1 was RII type. Out of 44 children who received the standard dose of 25 mg/kg, two (4.6%) were resistant (early RI type resistance). These data show for the first time the appearance of in vivo chloroquine resistance in this country, and call for a withdrawal of the 10 mg/kg dose of chloroquine in the treatment of fever attacks to the benefit of a 25 mg/kg dose. Thorough studies, using in vivo and in vitro techniques, should be undertaken as soon as possible, not only in Togo but in other West African countries too, to take the exact measure of the issue.