A review is made for the occurrence of bacterial diseases in cultured fin-fish in Ehime Prefecture from 1966 to 1992. In these 25 years, the production of marine fin-fish such as yellowtail Seriola quinqueradiata, red sea bream Pagrus major and Japanese flounder Paralichthys olivaceus has considerably increased in Ehime Prefecture. However, various kinds of diseases have occurred in these fish species, causing significant losses. About 60 ~ 90% of the disease cases of marine fin-fish diagnosed at Ehime Prefectural Fish Disease Control Center have been due to bacterial infections and major bacterial pathogens included Pasteurella piscicida (pseudotuberculosis) and Enterococcus seriolicida (streptococcicosis). Although chemotherapy with various antibiotics has been extensively applied to these two bacterial diseases, the amount of losses due to these diseases has not been reduced. The production efficiency of mariculture has become worse due to the expansion of prevalent period and host range in the two diseases and appearance of some new bacterial diseases.