Abstract: Purpose: To study whether 3,3'-dichlorobenzidine(DCB) can increase the tumor incidence in strain A mice. Methods: Strain A mice in 4 groups were orally administrated with DCB in 4 different dosages(64, 192, 576, 1 728 mg / kg) for 146 days. one month after stopping DCB, all the mice were killed and the viscera, especially the liver, lungs and kidneys were anatomically examined, and the tumors found in these organs were further pathologically examined. Results: There were benign tumors(lung adenoma, liver cholangioma) and malignant tumors(lung cancer, liver cholangiocarcinoma and hepatocellular carcinoma) in the lung and liver. The incidences of total tumors(51.1 ％) and malignant tumors(37.8 ％) of the higest dosage group were significantly higher than those of the control group(17.6 ％, 0)(P<0.01, P<0.05). Conclusion: DCB orally administrated at high dosage(136.2 mg / kg) can increase the malignant tumor incidence in strain A mice.

Key words: strain A mice, 3, 3'-dichlorobenzidine, tumor