During two full years - from October 1980 to September 1982 - we captured sandflies in the National Park of Serra dos Órgãos, State of Rio de Janeiro, Brazil. The captures, with human bait, were carried out weeklky, each with a duration of two hours, and at three different times (6 to 8 a.m., 5 to 7 a.m and 7:30 to 9:30 p.m.). In every capture, we recorded the phase of the moom and, at each hour, the temperature, relative humidity, wind and rain. In 586 hours 4,834 sandflies of ten species were captured, all blonging to genus Lutzomyia França, 1924. L. ayrozai and L. hirsuta represented 92% of the total species captured. However, they were dominant at different times, the former being more frequent in the warm and wet months, and considerably declining in the cold and dry months, in which the latter gradually prevailed. L. fischeri and L. shannoni were shown to be the most resistant to unfavourable weather conditions. Whenever there was any rain or wind, they were, in general, the only species captured. With regard to lunar cycle, we observed that new moom was the most favourable phase for the capture of sandflies and full moon the one with the smallest yield, except for L. shannoni which occurred more frequently during this period.