This parasitological research was conducted from September 2002 to August 2003 on the freshwater fishes in Zanjan province. Totally 155 fishes including Capoeta capoeta idellaI (91), Carassius auratus (8), Leuciscus cephalus (18), Ctenopharyngodon idella (10), Barbus lacerta (8), Allburnoides bipunctatus (10) and Alburnus filippi (10), were seined from five different stations. The fishes were transferred to Laboratory of Aquatic Organisms Research in Science Faculty of Shahid Beheshti University. The skin and gills of fishes were studied under light and stereomicroscope. The identified monogenean parasites included seven Dactylogyrus species as: D. chramuli, D. gracilis, D. Lenkorani and D. pulcher from Capoeta capoeta gracilis; D. lamellatus from Ctenopharyngodon idella; D. goktschaicus from Barbus lacerta and D. vistulae from Albunoides bipunctatus and Alburnus filippi. Various Gyrodactylus spp. from skin and gills of different fish specimens and one Paradiplozoon sp. from gill of Alburnoides bipunctatus were observed. This is the first parasitological investigation that has been done on the freshwater fishes of Zanjan province
