To explore the carcinogenic effects of sterigmatocystin(ST), one of the predominant contaminating mycotoxins in high risk areas of cancer in China, mutation of tumor suppressor gene p53 and oncogene Ki-ras in human fetal lung cells in vitro induced by ST was studied using cell culture and silver-staining PCR-SSCP methods. The results showed that, within 22 weeks of ST treatment, no abnormalities were found for both p53 and Ki-ras gene in electrophoresis. Abnormal electrophoretic migration bands were seen at exon 8 of p53 gene and Ki-ras gene in ST-treated human lung fibroblast cells 22 weeks after ST treatment. Thus, the results further confirmed the carcinogenic effects of ST on human fetal lung tissue.