The mosquito fauna has been studied in five Polish towns: Szczecin (31 species recorded), Świnoujście (23), Gdańsk (26), Warsaw (36) and Wrocław (18). In all five towns 38 mosquito species have been recorded. Thirteen species were present in each of the study towns - Anopheles maculipennis s.l., Aedes cinereus, Ae. vexans, Culex pipiens, Culiseta annulata, Ochlerotatus annulipes, Oc. cantans, Oc. caspius, Oc. cataphylla, Oc. communis, Oc. dorsalis, Oc. flavescens and Oc. leucomelas. Eight species were recorded in four towns: Anopheles claviger, Coquillet-tidia richiardii, Culiseta morsitans, Culex torrentium, Ochlerotatus excrucians, Oc. geniculatus, Oc. punctor and Oc. sticlicus. The results are coincident with observations from several other European towns of Russia, Czech Republic and Hungary. Species typical of Polish towns occur commonly in comparative European towns. All of the competent mosquito vectors of human diseases known in Poland were registered in urban fauna (34.2% species recorded) - most of them occurred numerously. It must be a factor, which increases the epidemiological hazard of mosquito-borne diseases in towns.