Abstract: Objective 　To explore the effects of oral administration of aflatoxin G₁ on SP-C and PCNA expression of alveolar epithelial cells in NIH mice. Methods 　NIH mice were randomly divided into three groups. Two experimental groups were treated int ragast rically by gavage with AFG₁ 3g/ kg and AFG₁ 30g/kg respectively, 3 times a week for 24 weeks. The mice in control group were correspondently treated with normal saline. All mice were fed with food that was free of AFGsas confirmed by HPLC analysis and then sacrificed and examined pathologically at the 58 weeks. The expression of SP-C and PCNA alveolar epithelial cells were determined by immunohistochemical staining. Results 　The immunohistochemical labelling index of SP-C of alveolar epithelial cells in AFG₁ 3g/ kg and AFG₁ 30g/ kg group were (31. 63 ±5. 51) % and (33. 58 ±4. 84) % respectively, which were significantly higher than that in control group (19. 72 ±1. 92) %, P < 0. 01. The labelling index of PCNA of alveolar epithelial cells in AFG₁ 3μg/ kg and AFG₁ 30μg/ kg group were significantly higher than that in cont rol group (27. 64 ±9. 22) % and (30. 08 ±9. 35) % vs (7. 91 ±1. 89) %, P < 0. 01. Conclusion 　Oral administ ration of AFG₁ can significantly increase the expression of SP-C and PCNA of alveolar epithelial cells in NIH mice.