Hispaniola has the highest malaria rate in the West Indies. A study of the bio-ecology of the major vector Anopheles albimanus was carried out in Haïti. Our observations concerned the length of pre-imaginal stages, biting rates and the gonotrophic cycle. A table of its complete life cycle, stage by stage, was produced as well as a graph illustrating its whole larval development in its natural habitat. Results in the field and insectarium were compared. In the laboratory, the development was shorter, except for pupae. The temperature was the main factor governing the length of pre-imaginal development. Preimaginal development decreased from 15 days in the field to 9 days in the insectarium whereas the temperature was a high of 4 degrees C. The nycthemeral activity and seasonal variations of An. albimanus were studied, by monthly all-night captures on human volunteers, during a full year in exo- and endophilic situations. Two sampling sites were chosen for comparison, An. albimanus were caught at every hour of the nycthemeral cycle, with a peak around midnight. Monthly variations were affected by the rains. The vector was more exophagous, when its density was high. The parity rate of the biting population varied between 85.8% and 20.0%; it was low at the beginning of the rains and increased when the rains stopped and breeding places dried out. To study the gonotrophic cycle of wild An. albimanus, several techniques were used jointly; follicles dissection; follicular relics; length of maturation of follicles. The length of the full cycle and of each of its components was estimated (quest of host for blood meal; maturation phase; breeding site seeking). In Haïti 41 h (nulliparous), or 21 h (parous) were necessary for females to have a complete maturation of the follicles. The lengthening of the gonotrophic cycle of parous An. albimanus, in the natural field site, was estimated to last about 4 days. For nulliparous it was 5 days, and 7 days if a pregravid stage was necessary. Considering the sporogonic cycle of Plasmodium falciparum (12 days), the wild population of An. albimanus females could become infective at the third blood feeding in Haïti.