In this study, the bacterial pathogen agents of cultivated rainbow trout (Oncorhynchus mykiss Walbaum) in Turkey were investigated. Pathogens from 692 samples belonging to 20 rainbow trout populations from different localities of Turkey were isolated between 2005 and 2008. 11 different bacterial pathogens were identified: Acinetobacter sp., Aeromonas hydrophila, Aer-omonas sobria, Citrobacter freundii, Flavobacterium psychrophilum, Lactococcus garvieae, Micrococcus luteus, Streptococcus iniae, Vibrio alginolyticus, Vibrio anguillarum, and Yer-sinia ruckeri. The most frequently isolated pathogen was Yersinia ruckeri. Disc diffusion method was used to determine antimicrobial susceptibility to several antibiotics. The isolates were found to be susceptible to enfrofloxacin, oxytetracycline and florfenicol.