During the Central African (Sahelian) drought, attacks of falciparum malaria were common in patients and their relatives shortly after their arrival in a hospital in Eastern Niger. A prospective study of 72 adult patients not admitted for malaria and 109 accompanying relatives was undertaken to investigate this observation. 23 attacks occurred in patients and 51 in relatives, with a peak frequency five days after arrival. On arrival, parasitaemia was low but reached a maximum by five days. Serum-iron and percentage saturation of transferrin were moderately increased initially, rose dramatically within forty-eight hours with near maximum saturation, and were falling by the fifth day. It is suggested that the early hyperferraemia, apparently related to refeeding, led to rapid multiplication of existing parasites and attacks of malaria. The results of experimental malarial infection of Wistar rats, half of which had been given intramuscular iron, supported this hypothesis.