The purpose of this study is to determine both clinical and histopathological changes in experimentally infected rainbow trout with Lactococcus garvieae. Fourty healthy fish samples (50-60 g in weight) were purchased from a commercial farm near Antalya, Turkey and transferred to the laboratory. Each group of fish were challenged a cell density of 6x10 5 cfu/ml of L. garvieae isolate. The control group was given with the appropriate dilution of the sterile PBS. Fish showed darkening of skin color, lesion on the upper jaw and prolapsus. Internally, they had pale liver and kidney, enlarged spleen and hemorrhagies on the muscle. The control group did not show clinical signs. Histopathologically, the kidney and liver showed haemosiderin deposits. Lamellar fusion and hyperplasia of primary lamellae in the gills, depletions of red and white pulpas in the spleen and necrosis of the gastro-intestinal tract were detected.