The biting indoor cycle of Anopheles gambiae s.s. was studied in a rural zone near Bouaké from 6 pm to 6 am. The cycle was characterized by a peak between midnight and 1 am (n = 19,181). The parturity rate of biting females regularly increased from 6 pm until 3 am, then remained at a high level up to 6 am (n = 14,239). Infected bites were observed from 7 pm to 6 am with a maximum between 0 and 3 am, and 96.7% of them were obtained between 11 pm and 4 am (n = 219). It appears that malaria transmission occurs essentially at the moment when villagers are in bed. The correct use of impregnated bed nets may thus greatly reduce malaria transmission.