This paper reported that the activation of oncogenes in human fetal esopha geal epithelium treated by alternariol (AOH). It was found that NIH/3T3 cells were transformed via transfeetion of DNA extracted from human fetal esophageal epithelium which was cultured and treated by 10?g/ml AOH in a short term in vitro. The efficiency of primary loci was 0.17 focus per ?g of DNA. In the secondary transfection, the efficiency was 0.58 focus per ?g of DNA (P