The authors report the results of 3 sample surveys carried out in Libreville, Ngounié and Haut-Ogooué Provinces to evaluate the main malarial indexes among 0 to 15 years old children in Gabon. These investigations would suggest that malaria is mesoendemic in the three areas. The systematic presumptive antimarial treatment of fever attacks is widely used in Libreville but not so frequent in rural areas.