The genotoxic potential of citric acid (CA) was studied using the micronucleus (MN) test in the erythrocytes of Tinca tinca. Three different doses (200 mg/L, 300 mg/L and 400 mg/L) of CA were applied to the fish for 24, 48, 72 and 96 h. Dechlorinated tap water served as a negative control. The frequencies of MN were elevated in a dose- and time-dependent manner in all treatments when compared to their respective controls. The incidence of micronucleated erythrocytes peaked at 400 mg/L concentration at 96 h exposure. All MN frequencies were significantly different from control (P<0.05). It is concluded that CA exerts genotoxic effect for Tinca tinca under the experimental conditions employed. In view of the present data, CA should be used with caution in food industry and further clarifying works are required to delineate its other possible genotoxic actions.