The intensive rearing of European eels are systematically developing in many countries. The immune system can be exposed to a variety of physical and chemical stressors. The aim of the present study was to determine the innate immunity in European eels growing in natural condition (in rivers) and intensive system of rearing. The analyses of the results showed that the metabolic activity of blood phagocytes, phagocytic ability (RBA) and potential killing activity (PKA) of blood and spleen phagocytes were higher in European eel from natural condition, compared to fish from intensive system of rearing. The similar pattern was observed in proliferative response of blood and pronephros lymphocytes stimulated by mitogens. Also the myeloperoxidase production by blood neutrophils was higher in eels from natural condition. The results of humoral mediated immunity showed that the lysozyme and ceruloplasmine activity in plasma and total Ig levels in serum were higher in eel from natural condition, compared to the fish from intensive culture. Only statistically significant lower levels of total protein in fish from natural condition were observed.