Systematic captures were conducted in the National Park of Serra dos Órgãos, state of Rio de janeiro, Brazil, during two consecutive years - September 1980 to August 1982 - with the purpose of establishing the seasonal distribution of local species of Culicidae using human bait. From the data collected, we believe that such distribution was directly influenced by three relevant climatological factors, in this order: rainfall, relative humidity and temperature. Winter acted asa limitting factor for most species. During this period, the Sabethini were the most resistant and, consequently, the most constant and abundant mosquitoes. The Sabethines Limatus durhami and Phoniomyia pilicauda were the most abundant mosquitoes, followed by the Culicinies Culex nigripalpus and Aedes scapularis. Some of the species found are known to be vectors of human diseases: llaemagogus capricornii, Ha. leucocelaenus, Anopheles cruzii and Aedes scapularis being among the most important. As to the Anophelini, An. cruzii was the predominanting species present.