Blood-feeding sources of Culex quinquefasciatus Say (Diptera: Culicidae) collected in theeasternregionoftheBrazilianstateofSantaCatarinawereanalyzedbyprecipitintechnique.One hundred Þfty-four female mosquitoes collected by CDC traps in the Navegantes municipality 13Ð15 February 2005 reacted to one or more of eight antisera, including chicken, dog, goat, sheep, horse, opossum,humanandrodentantisera.Onehundredthirty-sevenspecimens(89%)reactedtoonlyone source, and 17 (11%) specimens reacted to two sources. Among the 137 specimens reacting to only onesource,reactionstorodent(50.4%),sheep(5.8%),chicken(5.1%),goat(5.1%),dog(2.2%),horse (3.6%), and human (3.6%) antisera were observed. The analyzed species demonstrated a high degree of opportunistic feeding behavior in relation to host preference. Results are compared with results from similar studies, and the low proportion of reactions to human antisera is discussed.