The effect of short-term and long-term in vivo exposure to cadmium on the morphology of common carp erythrocytes was evaluated, and comparison of in vitro toxicity of various cadmium salts to these cells was also done. Juvenile carps were subjected to 3 h exposure at 6.5 mg/l or to a 4 week exposure at 0.65 mg/l of cadmium. Full blood was incubated for 2 h with cadmium chloride, sulfate, or nitrate at the concentration of 5 μl/ml of blood. All exposures resulted in a significant increase in frequency of abnormal erythrocytes. Anomalies included chromatin condensation at the nucleus border, nuclear malformation, cell body malformation, cytoplasm vacuolation, and swelling and hemolysis, with nuclear anomalies being the most frequent. In fish subjected to long-term cadmium exposure (and in some degree in fish after short-term exposure) an increase in erythroblast frequency occurred, which indicates hematological compensation for erythrocyte damage. A high percentage of abnormal erythrocytes observed under in vitro conditions (also in the control) indicates very high sensitivity of these cells to experimental factors. Cadmium nitrate induced more anomalies in carp erythrocytes (particularly nucleus malformations and cytoplasm vacuolation) than chloride and sulfate. The obtained results confirmed the genotoxic and cytotoxic properties of cadmium and showed that fish erythrocytes are good models for cytotoxicity studies.