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Objective:To establish the integrity experiment method of short(medium)-term carcinogenicity test pursuant to GLP, make into relative SOP and improve the safeguard in the center.Methods:Diethylinitrosamine(DEN) is known as carcinogenic agent,whose target organ is liver. Using the two-stage carcinogenesis test method, DEN was treated to F344 rats via intraperitoneal injection singly(200 mg/kg), and peros administrated for 90 days(10 ppm). The liver in any group rat will be examined by light microscopy.Results:In pathologic examination, no liver cell tumor was shown in the livers of the rats that were singly treated with a carcinogenic chemical-DEN.Foci of cellular alteration were observed in the livers of these rats. The proliferation lesions of liver from slight to seveity(foci of cellular alteration-hepatocelluar adenoma-hepatocellular carcinoma)were observed in the livers of the rats which exposed peros to a low dose of DEN for 90 days after initiation by a single intraperitoneal injection. The incidence of hepatocelluar tumor was 35% in male animal,which was not shown in the liver of female rat.Conclusion:For current results, it may be possible that low-dose DEN acts as a promotor of hepatocelluar tumor if it was exposed in a population for a long time. It is considered that male hormone has a synergistic effect on hepatocelluar tumor development of DEN. This two-stage carcinogenesis test might be a new model for the study of drug induced and promoted carcinogenesis,which could be used to evaluate the carcinogenesis of chemical compound fast.